Sécurité de la couche de transport

Transport Layer Security ( TLS ), le successeur de Secure Sockets Layer ( SSL ), désormais obsolète, est un protocole cryptographique conçu pour assurer la sécurité des communications sur un réseau informatique. Le protocole est largement utilisé dans des applications telles que la messagerie électronique , la messagerie instantanée et la voix sur IP , mais son utilisation pour sécuriser HTTPS reste la plus visible publiquement.

Le protocole TLS vise principalement à assurer la cryptographie , y compris la confidentialité (confidentialité), l’intégrité et l’authenticité grâce à l’utilisation de certificats , entre deux ou plusieurs applications informatiques communicantes. Il s’exécute dans la couche application et est lui-même composé de deux couches : l’enregistrement TLS et les protocoles de prise de contact TLS .

TLS est une norme proposée par l’Internet Engineering Task Force (IETF), définie pour la première fois en 1999, et la version actuelle est TLS 1.3, définie en août 2018. TLS s’appuie sur les spécifications SSL antérieures (1994, 1995, 1996) développées par Netscape Communications pour ajoutant le protocole HTTPS à leur navigateur Web Navigator.

La description

Les applications client-serveur utilisent le protocole TLS pour communiquer sur un réseau d’une manière conçue pour empêcher l’écoute clandestine et la falsification .

Comme les applications peuvent communiquer avec ou sans TLS (ou SSL), il est nécessaire que le client demande au serveur d’établir une connexion TLS. ^[1] L’un des principaux moyens d’y parvenir consiste à utiliser un numéro de port différent pour les connexions TLS. Par exemple, le port 80 est généralement utilisé pour le trafic HTTP non chiffré tandis que le port 443 est le port commun utilisé pour le trafic HTTPS chiffré. Un autre mécanisme consiste pour le client à faire une demande spécifique au protocole au serveur pour basculer la connexion vers TLS ; par exemple, en faisant une requête STARTTLS lors de l’utilisation des protocoles mail et news .

Une fois que le client et le serveur ont convenu d’utiliser TLS, ils négocient une connexion avec état en utilisant une procédure d’ établissement de liaison . ^[2] Les protocoles utilisent une poignée de main avec un chiffrement asymétrique pour établir non seulement les paramètres de chiffrement, mais également une clé partagée spécifique à la session avec laquelle la communication ultérieure est chiffrée à l’aide d’un chiffrement symétrique . Au cours de cette poignée de main, le client et le serveur s’accordent sur différents paramètres utilisés pour établir la sécurité de la connexion :

• La poignée de main commence lorsqu’un client se connecte à un serveur compatible TLS demandant une connexion sécurisée et que le client présente une liste des suites de chiffrement prises en charge ( chiffres et fonctions de hachage ).
• Dans cette liste, le serveur choisit une fonction de chiffrement et de hachage qu’il prend également en charge et informe le client de la décision.
• Le serveur fournit alors généralement une identification sous la forme d’un certificat numérique . Le certificat contient le nom du serveur , l’ autorité de certification (CA) de confiance qui garantit l’authenticité du certificat et la clé de cryptage publique du serveur.
• Le client confirme la validité du certificat avant de poursuivre.
• Pour générer les clés de session utilisées pour la connexion sécurisée, le client soit :
  • chiffre un nombre aléatoire ( PreMasterSecret ) avec la clé publique du serveur et envoie le résultat au serveur (que seul le serveur doit pouvoir déchiffrer avec sa clé privée) ; les deux parties utilisent ensuite le nombre aléatoire pour générer une clé de session unique pour le chiffrement et le déchiffrement ultérieurs des données pendant la session
  • utilise l’échange de clés Diffie-Hellman pour générer en toute sécurité une clé de session aléatoire et unique pour le chiffrement et le déchiffrement qui a la propriété supplémentaire de secret de transmission : si la clé privée du serveur est divulguée à l’avenir, elle ne peut pas être utilisée pour déchiffrer la session en cours, même si la session est interceptée et enregistrée par un tiers.

Ceci conclut la poignée de main et commence la connexion sécurisée, qui est chiffrée et déchiffrée avec la clé de session jusqu’à ce que la connexion se ferme. Si l’une des étapes ci-dessus échoue, la négociation TLS échoue et la connexion n’est pas créée.

TLS et SSL ne s’intègrent parfaitement dans aucune couche unique du modèle OSI ou du modèle TCP/IP . ^{[3] [4]} TLS s’exécute “au-dessus d’un protocole de transport fiable (par exemple, TCP)” ^[5] , ce qui impliquerait qu’il se trouve au-dessus de la couche de transport . Il sert de chiffrement aux couches supérieures, ce qui est normalement la fonction de la couche de présentation . Cependant, les applications utilisent généralement TLS comme s’il s’agissait d’une couche de transport, ^{[3] [4]} même si les applications utilisant TLS doivent contrôler activement l’initiation des poignées de main TLS et la gestion des certificats d’authentification échangés. ^[5]

Lorsqu’elles sont sécurisées par TLS, les connexions entre un client (par exemple, un navigateur Web) et un serveur (par exemple, wikipedia.org) doivent avoir une ou plusieurs des propriétés suivantes :

• La connexion est privée (ou sécurisée ) car un algorithme à clé symétrique est utilisé pour chiffrer les données transmises. Les clés de ce chiffrement symétrique sont générées de manière unique pour chaque connexion et sont basées sur un secret partagé qui a été négocié au début de la session. Le serveur et le client négocient les détails de l’algorithme de chiffrement et des clés cryptographiques à utiliser avant la transmission du premier octet de données (voir ci-dessous). La négociation d’un secret partagé est à la fois sécurisée (le secret négocié est inaccessible aux oreilles indiscrètes et ne peut être obtenu, même par un attaquant qui se place au milieu de la connexion) et fiable (aucun attaquant ne peut modifier les communications pendant la négociation sans être détecté).
• L’identité des parties communicantes peut être authentifiée à l’ aide de la cryptographie à clé publique . Cette authentification est obligatoire pour le serveur et facultative pour le client. ^[6]
• La connexion est fiable car chaque message transmis comprend une vérification de l’intégrité du message à l’aide d’un code d’authentification de message pour empêcher la perte ou l’altération non détectée des données pendant la transmission. ^{[7] : 3}

En plus de ce qui précède, une configuration minutieuse de TLS peut fournir des propriétés supplémentaires liées à la confidentialité, telles que le secret de transmission , garantissant que toute divulgation future de clés de chiffrement ne peut pas être utilisée pour déchiffrer des communications TLS enregistrées dans le passé.

TLS prend en charge de nombreuses méthodes différentes pour échanger des clés, chiffrer des données et authentifier l’intégrité des messages. Par conséquent, la configuration sécurisée de TLS implique de nombreux paramètres configurables, et tous les choix ne fournissent pas toutes les propriétés liées à la confidentialité décrites dans la liste ci-dessus (voir les tableaux ci-dessous § Échange de clé , § Sécurité du chiffrement et § Intégrité des données ).

Des tentatives ont été faites pour subvertir certains aspects de la sécurité des communications que TLS cherche à fournir, et le protocole a été révisé à plusieurs reprises pour faire face à ces menaces de sécurité. Les développeurs de navigateurs Web ont révisé à plusieurs reprises leurs produits pour se défendre contre les faiblesses de sécurité potentielles après leur découverte (voir l’historique de prise en charge TLS/SSL des navigateurs Web).

Histoire et développement

Protocoles SSL et TLS

Protocole	Publié	Statut
SSL 1.0	Inédit	Inédit
SSL 2.0	1995	Obsolète en 2011 ( RFC 6176 )
SSL 3.0	1996	Obsolète en 2015 ( RFC 7568 )
TLS 1.0	1999	Obsolète en 2021 ( RFC 8996 ) [8] [9] [10]
TLS 1.1	2006	Obsolète en 2021 ( RFC 8996 ) [8] [9] [10]
TLS 1.2	2008
TLS 1.3	2018

Système de réseau de données sécurisé

Le protocole TLS (Transport Layer Security Protocol), ainsi que plusieurs autres plates-formes de sécurité réseau de base, ont été développés dans le cadre d’une initiative conjointe lancée en août 1986 entre la National Security Agency, le National Bureau of Standards, la Defense Communications Agency et douze communications et sociétés informatiques qui ont lancé un projet spécial appelé Secure Data Network System (SDNS). ^[11]Le programme a été décrit en septembre 1987 lors de la 10e Conférence nationale sur la sécurité informatique dans un ensemble complet d’articles publiés. Le programme de recherche innovant s’est concentré sur la conception de la prochaine génération de réseaux de communication informatique sécurisés et de spécifications de produits à mettre en œuvre pour des applications sur des internets publics et privés. Il était destiné à compléter les nouvelles normes Internet OSI qui émergent rapidement, à la fois dans les profils GOSIP du gouvernement américain et dans l’énorme effort Internet ITU-ISO JTC1 au niveau international. Connu à l’origine sous le nom de protocole SP4, il a été renommé TLS puis publié en 1995 en tant que norme internationale ITU-T X.274 | ISO/CEI 10736:1995.

Programmation réseau sécurisée

Les premiers efforts de recherche vers la sécurité de la couche de transport comprenaient l’ interface de programmation d’application (API) Secure Network Programming (SNP) , qui en 1993 a exploré l’approche d’avoir une API de couche de transport sécurisée ressemblant étroitement aux sockets Berkeley , pour faciliter la mise à niveau des applications réseau préexistantes avec la sécurité. mesures. ^[12]

SSL 1.0, 2.0 et 3.0

Netscape a développé les protocoles SSL originaux, et Taher Elgamal , scientifique en chef chez Netscape Communications de 1995 à 1998, a été décrit comme le “père de SSL”. ^{[13] [14] [15] [16]}SSL version 1.0 n’a jamais été rendu public en raison de graves failles de sécurité dans le protocole. La version 2.0, après sa sortie en février 1995, s’est rapidement révélée contenir un certain nombre de failles de sécurité et de convivialité. Il utilisait les mêmes clés cryptographiques pour l’authentification et le chiffrement des messages. Il avait une construction MAC faible qui utilisait la fonction de hachage MD5 avec un préfixe secret, le rendant vulnérable aux attaques d’extension de longueur. Et il n’offrait aucune protection ni pour la poignée de main d’ouverture ni pour la fermeture d’un message explicite, ce qui signifiait que les attaques de l’homme du milieu pouvaient passer inaperçues. De plus, SSL 2.0 supposait un service unique et un certificat de domaine fixe, en conflit avec la fonctionnalité largement utilisée d’hébergement virtuel dans les serveurs Web, de sorte que la plupart des sites Web étaient effectivement empêchés d’utiliser SSL.

Ces failles ont nécessité la refonte complète du protocole vers SSL version 3.0. ^{[17] [15]} Sorti en 1996, il a été produit par Paul Kocher travaillant avec les ingénieurs de Netscape Phil Karlton et Alan Freier, avec une implémentation de référence par Christopher Allen et Tim Dierks de Consensus Development. Les nouvelles versions de SSL/TLS sont basées sur SSL 3.0. Le projet de 1996 de SSL 3.0 a été publié par l’IETF en tant que document historique dans la RFC 6101 .

SSL 2.0 a été déprécié en 2011 par RFC 6176 . En 2014, SSL 3.0 s’est avéré vulnérable à l’ attaque POODLE qui affecte tous les chiffrements par blocs dans SSL ; RC4 , le seul chiffrement non-bloc pris en charge par SSL 3.0, est également vraisemblablement cassé tel qu’il est utilisé dans SSL 3.0. ^[18] SSL 3.0 a été déprécié en juin 2015 par la RFC 7568 .

TLS 1.0

TLS 1.0 a été défini pour la première fois dans la RFC 2246 en janvier 1999 comme une mise à niveau de SSL version 3.0 et écrit par Christopher Allen et Tim Dierks de Consensus Development. Comme indiqué dans la RFC, “les différences entre ce protocole et SSL 3.0 ne sont pas dramatiques, mais elles sont suffisamment importantes pour empêcher l’interopérabilité entre TLS 1.0 et SSL 3.0”. Tim Dierks a écrit plus tard que ces changements, et le changement de nom de “SSL” en “TLS”, étaient un geste pour sauver la face de Microsoft, “donc il ne semblerait pas que l’IETF ne fasse qu’approuver le protocole de Netscape”. ^[19]

Le Conseil PCI a suggéré que les organisations migrent de TLS 1.0 vers TLS 1.1 ou supérieur avant le 30 juin 2018. ^{[20] [21]} En octobre 2018, Apple , Google , Microsoft et Mozilla ont annoncé conjointement qu’ils rendraient obsolètes TLS 1.0 et 1.1 en mars. 2020. ^[8]

TLS 1.1

TLS 1.1 a été défini dans la RFC 4346 en avril 2006. ^[22] Il s’agit d’une mise à jour de TLS version 1.0. Les différences significatives dans cette version incluent :

• Protection supplémentaire contre les attaques par chaînage de blocs de chiffrement (CBC).
  • Le vecteur d’initialisation implicite (IV) a été remplacé par un IV explicite.
  • Modification de la gestion des erreurs de remplissage .
• Prise en charge de l’ enregistrement IANA des paramètres. ^{[23] : 2}

La prise en charge des versions 1.0 et 1.1 de TLS a été largement dépréciée par les sites Web vers 2020, désactivant l’accès aux versions de Firefox avant 24 et aux navigateurs basés sur Chromium avant 29. ^{[24] [25] [26]}

TLS 1.2

TLS 1.2 a été défini dans la RFC 5246 en août 2008. Il est basé sur la spécification TLS 1.1 antérieure. Les principales différences incluent :

• La combinaison MD5 – SHA-1 dans la fonction pseudo -aléatoire (PRF) a été remplacée par SHA-256 , avec une option pour utiliser les PRF spécifiées par la suite de chiffrement .
• La combinaison MD5–SHA-1 dans le hachage de message fini a été remplacée par SHA-256, avec une option pour utiliser des algorithmes de hachage spécifiques à la suite de chiffrement. Cependant, la taille du hachage dans le message fini doit toujours être d’au moins 96 bits . ^[27]
• La combinaison MD5–SHA-1 dans l’élément signé numériquement a été remplacée par un seul hachage négocié lors de la poignée de main , qui est par défaut SHA-1.
• Amélioration de la capacité du client et du serveur à spécifier les hachages et les algorithmes de signature qu’ils acceptent.
• Extension de la prise en charge des chiffrements de chiffrement authentifiés , utilisés principalement pour le mode Galois/Counter Mode (GCM) et le mode CCM du chiffrement Advanced Encryption Standard (AES).
• La définition des extensions TLS et les suites de chiffrement AES ont été ajoutées. ^{[23] : 2}

Toutes les versions de TLS ont été affinées dans la RFC 6176 en mars 2011, supprimant leur rétrocompatibilité avec SSL de sorte que les sessions TLS ne négocient jamais l’utilisation de la version 2.0 de Secure Sockets Layer (SSL).

TLS 1.3

TLS 1.3 a été défini dans la RFC 8446 en août 2018. Il est basé sur la spécification TLS 1.2 antérieure. Les principales différences par rapport à TLS 1.2 incluent : ^[28]

• Séparer les algorithmes d’accord de clé et d’authentification des suites de chiffrement
• Suppression de la prise en charge des courbes elliptiques nommées faibles et moins utilisées
• Suppression de la prise en charge des fonctions de hachage cryptographique MD5 et SHA-224
• Exiger des signatures numériques même lorsqu’une configuration précédente est utilisée
• Intégration de HKDF et de la proposition DH semi-éphémère
• Remplacement de la reprise par PSK et tickets
• Prise en charge des poignées de main 1- RTT et prise en charge initiale de 0- RTT
• Mandater le secret de transmission parfait , au moyen de l’utilisation de clés éphémères lors de l’accord de clé (EC) DH
• Suppression de la prise en charge de nombreuses fonctionnalités non sécurisées ou obsolètes, notamment la compression , la renégociation, les chiffrements non AEAD , l’échange de clés non PFS (parmi lesquels les échanges de clés RSA statiques et DH statiques ), les groupes DHE personnalisés , la négociation du format de point EC, le protocole Change Cipher Spec, Heure UNIX du message Hello et entrée AD du champ de longueur dans les chiffrements AEAD
• Interdire la négociation SSL ou RC4 pour la rétrocompatibilité
• Intégration de l’utilisation du hachage de session
• Dépréciation de l’utilisation du numéro de version de la couche d’enregistrement et gel du numéro pour une meilleure rétrocompatibilité
• Déplacer certains détails d’algorithme liés à la sécurité d’une annexe à la spécification et reléguer ClientKeyShare à une annexe
• Ajout du chiffrement de flux ChaCha20 avec le code d’authentification de message Poly1305
• Ajout des algorithmes de signature numérique Ed25519 et Ed448
• Ajout des protocoles d’échange de clés X25519 et X448
• Ajout de la prise en charge de l’envoi de plusieurs réponses OCSP
• Chiffrement de tous les messages de poignée de main après le ServerHello

Network Security Services (NSS), la bibliothèque de cryptographie développée par Mozilla et utilisée par son navigateur Web Firefox , a activé TLS 1.3 par défaut en février 2017. ^[29] La prise en charge de TLS 1.3 a ensuite été ajoutée — mais en raison de problèmes de compatibilité pour un petit nombre de utilisateurs, pas automatiquement activés ^[30] — à Firefox 52.0 , sorti en mars 2017. TLS 1.3 a été activé par défaut en mai 2018 avec la sortie de Firefox 60.0 . ^[31]

Google Chrome a défini TLS 1.3 comme version par défaut pendant une courte période en 2017. Il l’a ensuite supprimé par défaut, en raison de boîtiers de médiation incompatibles tels que les proxies Web Blue Coat . ^[32]

Lors de l’IETF 100 Hackathon , qui s’est déroulé à Singapour en 2017, le groupe TLS a travaillé sur l’adaptation d’applications open source pour utiliser TLS 1.3. ^{[33] [34]} Le groupe TLS était composé d’individus du Japon, du Royaume-Uni et de Maurice via l’équipe cyberstorm.mu. ^[34] Ce travail a été poursuivi dans le Hackathon IETF 101 à Londres , ^[35] et le Hackathon IETF 102 à Montréal. ^[36]

wolfSSL a permis l’utilisation de TLS 1.3 à partir de la version ^3.11.1 , publiée en mai 2017 ^. ainsi que de nombreuses versions plus anciennes. Une série de blogs ont été publiés sur la différence de performances entre TLS 1.2 et 1.3. ^[39]

DansSeptembre 2018, le projet populaire OpenSSL a publié la version 1.1.1 de sa bibliothèque, dans laquelle la prise en charge de TLS 1.3 était “la nouvelle fonctionnalité phare”. ^[40]

La prise en charge de TLS 1.3 a été ajoutée pour la première fois à SChannel avec Windows 11 et Windows Server 2022 . ^[41]

Sécurité des transports d’entreprise

L’ Electronic Frontier Foundation a fait l’ éloge de TLS 1.3 et s’est dite préoccupée par la variante de protocole Enterprise Transport Security (ETS) qui désactive intentionnellement d’importantes mesures de sécurité dans TLS 1.3. ^[42] Initialement appelé Enterprise TLS (eTLS), ETS est une norme publiée connue sous le nom de « ETSI TS103523-3 », « Middlebox Security Protocol, Part3 : Enterprise Transport Security ». Il est destiné à être utilisé entièrement dans des réseaux propriétaires tels que des systèmes bancaires. ETS ne prend pas en charge la confidentialité persistante afin de permettre aux organisations tierces connectées aux réseaux propriétaires de pouvoir utiliser leur clé privée pour surveiller le trafic réseau afin de détecter les logiciels malveillants et de faciliter la réalisation d’audits. ^{[43] [44]}Malgré les avantages revendiqués, l’EFF a averti que la perte du secret de transmission pourrait faciliter l’exposition des données tout en affirmant qu’il existe de meilleures façons d’analyser le trafic.

Certificats numériques

Exemple de site web avec certificat numérique

Un certificat numérique certifie la propriété d’une clé publique par le sujet nommé du certificat et indique certaines utilisations attendues de cette clé. Cela permet à d’autres (parties utilisatrices) de s’appuyer sur des signatures ou sur des affirmations faites par la clé privée qui correspond à la clé publique certifiée. Les magasins de clés et les magasins de confiance peuvent être dans différents formats, tels que .pem, .crt, .pfx et .jks.

Autorités de certification

TLS s’appuie généralement sur un ensemble d’autorités de certification tierces de confiance pour établir l’authenticité des certificats. La confiance est généralement ancrée dans une liste de certificats distribués avec un logiciel d’agent utilisateur ^[45] et peut être modifiée par la partie utilisatrice.

Selon Netcraft , qui surveille les certificats TLS actifs, l’autorité de certification (CA) leader du marché est Symantec depuis le début de leur enquête (ou VeriSign avant que l’unité commerciale des services d’authentification ne soit achetée par Symantec). En 2015, Symantec représentait un peu moins d’un tiers de tous les certificats et 44 % des certificats valides utilisés par les 1 million de sites Web les plus fréquentés, selon Netcraft. ^[46] En 2017, Symantec a vendu son activité TLS/SSL à DigiCert. ^[47] Dans un rapport mis à jour, il a été montré qu’IdenTrust , DigiCert et Sectigo sont les 3 principales autorités de certification en termes de part de marché depuis mai 2019.^[48]

En conséquence du choix des certificats X.509 , des autorités de certification et une infrastructure à clé publique sont nécessaires pour vérifier la relation entre un certificat et son propriétaire, ainsi que pour générer, signer et administrer la validité des certificats. Bien que cela puisse être plus pratique que de vérifier les identités via un réseau de confiance , les divulgations de surveillance de masse de 2013 ont fait savoir plus largement que les autorités de certification sont un point faible du point de vue de la sécurité, permettant des attaques de l’homme du milieu (MITM) si l’autorité de certification coopère (ou est compromise). ^{[49] [50]}

Algorithmes

Échange de clé ou accord de clé

Avant qu’un client et un serveur puissent commencer à échanger des informations protégées par TLS, ils doivent échanger ou convenir en toute sécurité d’une clé de chiffrement et d’un chiffrement à utiliser lors du chiffrement des données (voir § Chiffrement ). Parmi les méthodes utilisées pour l’échange/l’accord de clés figurent : les clés publiques et privées générées avec RSA (notées TLS_RSA dans le protocole de prise de contact TLS), Diffie–Hellman (TLS_DH), Diffie–Hellman éphémère (TLS_DHE), Diffie–Hellman à courbe elliptique ( TLS_ECDH), Diffie–Hellman à courbe elliptique éphémère (TLS_ECDHE), Diffie–Hellman anonyme (TLS_DH_anon), ^[7] clé pré-partagée (TLS_PSK) ^[51] et Secure Remote Password (TLS_SRP). ^[52]

Les méthodes d’accord de clé TLS_DH_anon et TLS_ECDH_anon n’authentifient pas le serveur ou l’utilisateur et sont donc rarement utilisées car elles sont vulnérables aux attaques de type ” man-in-the-middle” . Seuls TLS_DHE et TLS_ECDHE fournissent le secret de transmission .

Les certificats de clé publique utilisés pendant l’échange/l’accord varient également dans la taille des clés de chiffrement publiques/privées utilisées pendant l’échange et donc la robustesse de la sécurité fournie. En juillet 2013, Google a annoncé qu’il n’utiliserait plus de clés publiques de 1024 bits et passerait à la place à des clés de 2048 bits pour augmenter la sécurité du cryptage TLS qu’il fournit à ses utilisateurs car la force de cryptage est directement liée à la taille de la clé. . ^{[53] [54]}

Échange de clé/accord et authentification

Algorithme	SSL 2.0	SSL 3.0	TLS 1.0	TLS 1.1	TLS 1.2	TLS 1.3	Statut
RSA	Oui	Oui	Oui	Oui	Oui	Non	Défini pour TLS 1.2 dans les RFC
DH – RSA	Non	Oui	Oui	Oui	Oui	Non
DHE – RSA ( secret de transmission )	Non	Oui	Oui	Oui	Oui	Oui
ECDH – RSA	Non	Non	Oui	Oui	Oui	Non
ECDHE – RSA (secret transmis)	Non	Non	Oui	Oui	Oui	Oui
DH – DSS	Non	Oui	Oui	Oui	Oui	Non
DHE – DSS (secret de transmission)	Non	Oui	Oui	Oui	Oui	Non [55]
ECDH – ECDSA	Non	Non	Oui	Oui	Oui	Non
ECDHE – ECDSA (secret transmis)	Non	Non	Oui	Oui	Oui	Oui
ECDH – EdDSA	Non	Non	Oui	Oui	Oui	Non
ECDHE – EdDSA (secret transmis) [56]	Non	Non	Oui	Oui	Oui	Oui
PSK	Non	Non	Oui	Oui	Oui
PSK – RSA	Non	Non	Oui	Oui	Oui
DHE – PSK (secret de transmission)	Non	Non	Oui	Oui	Oui	Oui
ECDHE – PSK (secret transmis)	Non	Non	Oui	Oui	Oui	Oui
PRS	Non	Non	Oui	Oui	Oui
SRP – DSS	Non	Non	Oui	Oui	Oui
SRP – RSA	Non	Non	Oui	Oui	Oui
KerberosName	Non	Non	Oui	Oui	Oui
DH -ANON (non sécurisé)	Non	Oui	Oui	Oui	Oui
ECDH -ANON (non sécurisé)	Non	Non	Oui	Oui	Oui
GOST R 34.10-94 / 34.10-2001 [57]	Non	Non	Oui	Oui	Oui	Proposé dans les brouillons RFC

Chiffrer

Sécurité chiffrée contre les attaques réalisables connues du public

Chiffrer	Version du protocole	Statut
Taper	Algorithme	Force nominale (bits)	SSL 2.0	SSL 3.0 [n 1] [n 2] [n 3] [n 4]	TLS 1.0 [n 1] [n 3]	TLS 1.1 [n 1]	TLS 1.2 [n 1]	TLS 1.3
Chiffrement par bloc avec mode de fonctionnement	MCG AES [58] [n 5]	256, 128	N / A	N / A	N / A	N / A	Sécurise	Sécurise	Défini pour TLS 1.2 dans les RFC
AES CCM [59] [n 5]	N / A	N / A	N / A	N / A	Sécurise	Sécurise
AES SRC [n 6]	N / A	Précaire	Dépend des atténuations	Dépend des atténuations	Dépend des atténuations	N / A
Camélia GCM [60] [n 5]	256, 128	N / A	N / A	N / A	N / A	Sécurise	N / A
Camélia CBC [61] [n 6]	N / A	Précaire	Dépend des atténuations	Dépend des atténuations	Dépend des atténuations	N / A
MCG ARIA [62] [n 5]	256, 128	N / A	N / A	N / A	N / A	Sécurise	N / A
ARIA CBC [62] [n 6]	N / A	N / A	Dépend des atténuations	Dépend des atténuations	Dépend des atténuations	N / A
SEED CTF [63] [n 6]	128	N / A	Précaire	Dépend des atténuations	Dépend des atténuations	Dépend des atténuations	N / A
3DES EDE CBC [n 6] [n 7]	112 [n 8]	Précaire	Précaire	Précaire	Précaire	Précaire	N / A
GOST 28147-89 CNT [57] [n 7]	256	N / A	N / A	Précaire	Précaire	Précaire	N / A	Défini dans la RFC 4357
IDÉE CBC [n 6] [n 7] [n 9]	128	Précaire	Précaire	Précaire	Précaire	N / A	N / A	Supprimé de TLS 1.2
DES CBC [n 6] [n 7] [n 9]	0 56	Précaire	Précaire	Précaire	Précaire	N / A	N / A
0 40 [n 10]	Précaire	Précaire	Précaire	N / A	N / A	N / A	Interdit dans TLS 1.1 et versions ultérieures
RC2 SRC [n 6] [n 7]	0 40 [n 10]	Précaire	Précaire	Précaire	N / A	N / A	N / A
Chiffrement de flux	ChaCha20 – Poly1305 [68] [n 5]	256	N / A	N / A	N / A	N / A	Sécurise	Sécurise	Défini pour TLS 1.2 dans les RFC
RC4 [n 11]	128	Précaire	Précaire	Précaire	Précaire	Précaire	N / A	Interdit dans toutes les versions de TLS par RFC 7465
0 40 [n 10]	Précaire	Précaire	Précaire	N / A	N / A	N / A
Rien	Nul [n 12]	–	Précaire	Précaire	Précaire	Précaire	Précaire	N / A	Défini pour TLS 1.2 dans les RFC

Remarques

1. ^ ^{a b c d} RFC 5746 doit être implémenté pour corriger un défaut de renégociation qui autrement casserait ce protocole.
2. ^ Si les bibliothèques implémentent les correctifs répertoriés dans RFC 5746 , cela viole la spécification SSL 3.0, que l’IETF ne peut pas modifier contrairement à TLS. La plupart des bibliothèques actuelles implémentent le correctif et ignorent la violation qui en résulte.
3. ^ ^{a b} L’ attaque BEAST brise tous les chiffrements par blocs (chiffres CBC) utilisés dans SSL 3.0 et TLS 1.0 à moins qu’ils ne soient atténués par le client et/ou le serveur. Voir § Navigateurs Web .
4. ^ L’ attaque POODLE brise tous les chiffrements par blocs (chiffres CBC) utilisés dans SSL 3.0 à moins qu’ils ne soient atténués par le client et/ou le serveur. Voir § Navigateurs Web .
5. ^ ^{a b c d e} Les chiffrements AEAD (tels que GCM et CCM ) ne peuvent être utilisés que dans TLS 1.2 ou version ultérieure.
6. ^ ^{a b c d e f g h} Les chiffrements CBC peuvent être attaqués avec l’ attaque Lucky Thirteen si la bibliothèque n’est pas écrite avec soin pour éliminer les canaux latéraux de synchronisation.
7. ^ ^{a b c d e} L’ attaque Sweet32 brise les chiffrements par bloc avec une taille de bloc de 64 bits. ^[64]
8. ^ Bien que la longueur de clé de 3DES soit de 168 bits, la force de sécurité effective de 3DES n’est que de 112 bits, ^[65] ce qui est inférieur au minimum recommandé de 128 bits. ^[66]
9. ^ ^{a b} IDEA et DES ont été supprimés de TLS 1.2. ^[67]
10. ^ ^{a b c} Des suites de chiffrement de 40 bits ont été intentionnellement conçues avec des longueurs de clé réduites pour se conformer aux réglementations américaines annulées depuis interdisant l’exportation de logiciels cryptographiques contenant certains algorithmes de chiffrement puissants (voir Exportation de cryptographie des États-Unis ). Ces suites faibles sont interdites dans TLS 1.1 et versions ultérieures.
11. ^ L’utilisation de RC4 dans toutes les versions de TLS est interdite par la RFC 7465 (car les attaques RC4 affaiblissent ou cassent RC4 utilisé dans SSL/TLS).
12. ^ Authentification uniquement, pas de cryptage.

Intégrité des données

Un code d’authentification de message (MAC) est utilisé pour l’intégrité des données. HMAC est utilisé pour le mode CBC des chiffrements par blocs. Le chiffrement authentifié (AEAD) tel que le mode GCM et le mode CCM utilise le MAC intégré à AEAD et n’utilise pas le HMAC . ^[69] PRF basé sur HMAC ou HKDF est utilisé pour la prise de contact TLS.

Intégrité des données

Algorithme	SSL 2.0	SSL 3.0	TLS 1.0	TLS 1.1	TLS 1.2	TLS 1.3	Statut
HMAC – MD5	Oui	Oui	Oui	Oui	Oui	Non	Défini pour TLS 1.2 dans les RFC
HMAC – SHA1	Non	Oui	Oui	Oui	Oui	Non
HMAC – SHA256/384	Non	Non	Non	Non	Oui	Non
AEAD	Non	Non	Non	Non	Oui	Oui
GOST 28147-89 IMIT [57]	Non	Non	Oui	Oui	Oui	Proposé dans les brouillons RFC
GOST R 34.11-94 [57]	Non	Non	Oui	Oui	Oui

Candidatures et adoption

Dans la conception d’applications, TLS est généralement implémenté au-dessus des protocoles de la couche de transport, cryptant toutes les données liées au protocole de protocoles tels que HTTP , FTP , SMTP , NNTP et XMPP .

Historiquement, TLS a été utilisé principalement avec des protocoles de transport fiables tels que le protocole TCP ( Transmission Control Protocol ). Cependant, il a également été implémenté avec des protocoles de transport orientés datagramme, tels que le protocole de datagramme utilisateur (UDP) et le protocole de contrôle de congestion de datagramme (DCCP), dont l’utilisation a été normalisée indépendamment en utilisant le terme Datagram Transport Layer Security (DTLS) .

Sites Internet

L’une des principales utilisations de TLS consiste à sécuriser le trafic World Wide Web entre un site Web et un navigateur Web codé avec le protocole HTTP. Cette utilisation de TLS pour sécuriser le trafic HTTP constitue le protocole HTTPS . ^[70]

Prise en charge du protocole de site Web (octobre 2021)

Version du protocole	Prise en charge du site Web [71]	Sécurité [71] [72]
SSL 2.0	0,4 %	Précaire
SSL 3.0	3,0 %	Insécurisé [73]
TLS 1.0	43,8 %	Obsolète [8] [9] [10]
TLS 1.1	47,8 %	Obsolète [8] [9] [10]
TLS 1.2	99,6 %	Dépend du chiffrement [n 1] et des atténuations du client [n 2]
TLS 1.3	49,7 %	Sécurise

Remarques

1. ^ voir § Table de chiffrement ci-dessus
2. ^ voir § Navigateurs Web etsections TLS/SSL

Navigateurs Web

Depuis avril 2016 ^[update], les dernières versions de tous les principaux navigateurs Web prennent en charge TLS 1.0, 1.1 et 1.2, et les ont activés par défaut. Cependant, tous les systèmes d’exploitation Microsoft pris en charge ne prennent pas en charge la dernière version d’IE. De plus, de nombreux systèmes d’exploitation Microsoft prennent actuellement en charge plusieurs versions d’IE, mais cela a changé selon la FAQ sur la politique de cycle de vie de la prise en charge d’Internet Explorer de Microsoft., “à compter du 12 janvier 2016, seule la version la plus récente d’Internet Explorer disponible pour un système d’exploitation pris en charge recevra une assistance technique et des mises à jour de sécurité.” La page continue ensuite en répertoriant la dernière version prise en charge d’IE à cette date pour chaque système d’exploitation. La prochaine date critique serait le moment où un système d’exploitation atteint la fin de la phase de vie, qui figure dans la fiche d’information sur le cycle de vie de Windows de Microsoft .

Les atténuations contre les attaques connues ne suffisent pas encore :

• Atténuations contre l’attaque POODLE : certains navigateurs empêchent déjà le repli vers SSL 3.0 ; cependant, cette atténuation doit être prise en charge non seulement par les clients, mais également par les serveurs. La désactivation de SSL 3.0 lui-même, la mise en œuvre du “fractionnement d’enregistrements anti-POODLE” ou le refus des chiffrements CBC dans SSL 3.0 sont nécessaires.
  • Google Chrome : complet (TLS_FALLBACK_SCSV est implémenté depuis la version 33, le retour à SSL 3.0 est désactivé depuis la version 39, SSL 3.0 lui-même est désactivé par défaut depuis la version 40. Le support de SSL 3.0 lui-même a été abandonné depuis la version 44.)
  • Mozilla Firefox : complet (le support de SSL 3.0 lui-même est abandonné depuis la version 39 . SSL 3.0 lui-même est désactivé par défaut et les retours vers SSL 3.0 sont désactivés depuis la version 34 , TLS_FALLBACK_SCSV est implémenté depuis la version 35. Dans ESR, SSL 3.0 lui-même est désactivé par par défaut et TLS_FALLBACK_SCSV est implémenté depuis ESR 31.3.)
  • Internet Explorer : partiel (uniquement dans la version 11, SSL 3.0 est désactivé par défaut depuis avril 2015. Les versions 10 et antérieures sont toujours vulnérables contre POODLE.)
  • Opera : complet (TLS_FALLBACK_SCSV est implémenté depuis la version 20, “anti-POODLE record splitting”, qui n’est efficace qu’avec l’implémentation côté client, est implémenté depuis la version 25, SSL 3.0 lui-même est désactivé par défaut depuis la version 27. Support de SSL 3.0 lui-même sera abandonné depuis la version 31.)
  • Safari : complet (uniquement sur OS X 10.8 et versions ultérieures et iOS 8, les chiffrements CBC lors du retour à SSL 3.0 sont refusés, mais cela signifie qu’il utilisera RC4, ce qui n’est pas non plus recommandé. La prise en charge de SSL 3.0 lui-même est abandonnée sur OS X 10.11 et versions ultérieures et iOS 9.)
• Atténuation contre les attaques RC4 :
  • Google Chrome a désactivé RC4 sauf en tant que solution de secours depuis la version 43. RC4 est désactivé depuis Chrome 48.
  • Firefox a désactivé RC4 sauf en tant que solution de secours depuis la version 36. Firefox 44 a désactivé RC4 par défaut.
  • Opera a désactivé RC4 sauf en tant que solution de secours depuis la version 30. RC4 est désactivé depuis Opera 35.
  • Internet Explorer pour Windows 7 / Server 2008 R2 et pour Windows 8 / Server 2012 a défini la priorité de RC4 sur la plus basse et peut également désactiver RC4, sauf en tant que solution de secours via les paramètres de registre. Internet Explorer 11 Mobile 11 pour Windows Phone 8.1 désactive RC4 sauf comme solution de secours si aucun autre algorithme activé ne fonctionne. Edge et IE 11 désactivent complètement RC4 en août 2016.
• Atténuation contre l’attaque FREAK :
  • Le navigateur Android inclus avec Android 4.0 et les versions antérieures est toujours vulnérable à l’attaque FREAK.
  • Internet Explorer 11 Mobile est toujours vulnérable à l’attaque FREAK.
  • Google Chrome, Internet Explorer (ordinateur de bureau), Safari (ordinateur de bureau et mobile) et Opera (mobile) ont mis en place des mesures d’atténuation FREAK.
  • Mozilla Firefox sur toutes les plateformes et Google Chrome sur Windows n’ont pas été affectés par FREAK.

Historique de prise en charge TLS/SSL des navigateurs Web

Navigateur	Version	Plateformes	Protocoles SSL	Protocoles TLS	Prise en charge des certificats	Vulnérabilités corrigées [n 1]	Sélection du protocole par l’utilisateur [n 2]
SSL 2.0 (non sécurisé)	SSL 3.0 (non sécurisé)	TLS 1.0 (obsolète)	TLS 1.1 (obsolète)	TLS 1.2	TLS 1.3	EV [n 3] [74]	SHA-2 [75]	ECDSA [76]	BÊTE [n 4]	CRIMINALITÉ [n 5]	CANICHE (SSLv3) [n 6]	RC4 [n 7]	FRÉQUENCE [77] [78]	Embâcle
Google Chrome ( Chrome pour Android ) [n 8] [n 9]	1–9	Windows (7+) macOS (10.11+) Linux Android (5.0+) iOS (12.2+) Chrome OS	Désactivé par défaut	Activé par défaut	Oui	Non	Non	Non	Oui (ordinateur de bureau uniquement)	nécessite un système d’exploitation compatible SHA-2 [75]	nécessite un système d’exploitation compatible ECC [76]	Non affecté [83]	Vulnérable (HTTPS)	Vulnérable	Vulnérable	Vulnérable (sauf Windows)	Vulnérable	Oui [n 10]
10–20	Non [84]	Activé par défaut	Oui	Non	Non	Non	Oui (ordinateur de bureau uniquement)	nécessite un système d’exploitation compatible SHA-2 [75]	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Vulnérable (HTTPS/SPDY)	Vulnérable	Vulnérable	Vulnérable (sauf Windows)	Vulnérable	Oui [n 10]
21	Non	Activé par défaut	Oui	Non	Non	Non	Oui (ordinateur de bureau uniquement)	nécessite un système d’exploitation compatible SHA-2 [75]	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Atténué [85]	Vulnérable	Vulnérable	Vulnérable (sauf Windows)	Vulnérable	Oui [n 10]
22–29	Non	Activé par défaut	Oui	Oui [86]	Non [86] [87] [88] [89]	Non	Oui (ordinateur de bureau uniquement)	nécessite un système d’exploitation compatible SHA-2 [75]	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Atténué	Vulnérable	Vulnérable	Vulnérable (sauf Windows)	Vulnérable	Temporaire [n 11]
30–32	Non	Activé par défaut	Oui	Oui	Oui [87] [88] [89]	Non	Oui (ordinateur de bureau uniquement)	nécessite un système d’exploitation compatible SHA-2 [75]	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Atténué	Vulnérable	Vulnérable	Vulnérable (sauf Windows)	Vulnérable	Temporaire [n 11]
33–37	Non	Activé par défaut	Oui	Oui	Oui	Non	Oui (ordinateur de bureau uniquement)	nécessite un système d’exploitation compatible SHA-2 [75]	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Atténué	Partiellement atténué [n 12]	Priorité la plus basse [92] [93] [94]	Vulnérable (sauf Windows)	Vulnérable	Temporaire [n 11]
38, 39	Non	Activé par défaut	Oui	Oui	Oui	Non	Oui (ordinateur de bureau uniquement)	Oui	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Atténué	Partiellement atténué	Priorité la plus basse	Vulnérable (sauf Windows)	Vulnérable	Temporaire [n 11]
40	Non	Désactivé par défaut [91] [95]	Oui	Oui	Oui	Non	Oui (ordinateur de bureau uniquement)	Oui	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Atténué	Atténué [n 13]	Priorité la plus basse	Vulnérable (sauf Windows)	Vulnérable	Oui [n 14]
41, 42	Non	Désactivé par défaut	Oui	Oui	Oui	Non	Oui (ordinateur de bureau uniquement)	Oui	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Atténué	Atténué	Priorité la plus basse	Atténué	Vulnérable	Oui [n 14]
43	Non	Désactivé par défaut	Oui	Oui	Oui	Non	Oui (ordinateur de bureau uniquement)	Oui	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Atténué	Atténué	Uniquement comme solution de repli [n 15] [96]	Atténué	Vulnérable	Oui [n 14]
44–47	Non	Non [97]	Oui	Oui	Oui	Non	Oui (ordinateur de bureau uniquement)	Oui	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Atténué	Pas affecté	Uniquement comme repli [n 15]	Atténué	Atténué [98]	Temporaire [n 11]
48, 49	Non	Non	Oui	Oui	Oui	Non	Oui (ordinateur de bureau uniquement)	Oui	nécessite un système d’exploitation compatible ECC [76]	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16] [99] [100]	Atténué	Atténué	Temporaire [n 11]
50–53	Non	Non	Oui	Oui	Oui	Non	Oui (ordinateur de bureau uniquement)	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16] [99] [100]	Atténué	Atténué	Temporaire [n 11]
54–66	Non	Non	Oui	Oui	Oui	Désactivé par défaut (version brouillon)	Oui (ordinateur de bureau uniquement)	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16] [99] [100]	Atténué	Atténué	Temporaire [n 11]
67–69	Non	Non	Oui	Oui	Oui	Oui (version préliminaire)	Oui (ordinateur de bureau uniquement)	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16] [99] [100]	Atténué	Atténué	Temporaire [n 11]
70–83	Non	Non	Oui	Oui	Oui	Oui	Oui (ordinateur de bureau uniquement)	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16] [99] [100]	Atténué	Atténué	Temporaire [n 11]
84–90	Non	Non	Avertir par défaut	Avertir par défaut	Oui	Oui	Oui (ordinateur de bureau uniquement)	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16] [99] [100]	Atténué	Atténué	Temporaire [n 11]
91–99	Non	Non	Non [101]	Non [101]	Oui	Oui	Oui (ordinateur de bureau uniquement)	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16] [99] [100]	Atténué	Atténué	Temporaire [n 11]
ESC 100	101
Navigateur	Version	Plateformes	SSL 2.0 (non sécurisé)	SSL 3.0 (non sécurisé)	TLS 1.0 (obsolète)	TLS 1.1 (obsolète)	TLS 1.2	TLS 1.3	Certificat VE	Certificat SHA-2	Certificat ECDSA	LA BÊTE	LA CRIMINALITÉ	CANICHE (SSLv3)	RC4	MONSTRE	Embâcle	Sélection du protocole par l’utilisateur
Microsoft Edge (basé sur Chromium) indépendant du système d’exploitation	79–83	Windows (7+) macOS (10.12+) Linux Android (4.4+) iOS (11.0+)	Non	Non	Oui	Oui	Oui	Oui	Oui	Oui	Oui	Atténué	Pas affecté	Pas affecté	Désactivé par défaut	Atténué	Atténué	Oui [n 10]
84–90	Non	Non	Avertir par défaut	Avertir par défaut	Oui	Oui	Oui	Oui	Oui	Atténué	Pas affecté	Pas affecté	Désactivé par défaut	Atténué	Atténué	Oui [n 10]
91-99	Non	Non	Non [102]	Non [102]	Oui	Oui	Oui	Oui	Oui	Atténué	Pas affecté	Pas affecté	Désactivé par défaut	Atténué	Atténué	Oui [n 10]
ESC 100	101
Navigateur	Version	Plateformes	SSL 2.0 (non sécurisé)	SSL 3.0 (non sécurisé)	TLS 1.0 (obsolète)	TLS 1.1 (obsolète)	TLS 1.2	TLS 1.3	Certificat VE	Certificat SHA-2	Certificat ECDSA	LA BÊTE	LA CRIMINALITÉ	CANICHE (SSLv3)	RC4	MONSTRE	Embâcle	Sélection du protocole par l’utilisateur
Mozilla Firefox ( Firefox pour mobile ) [n 17]	1.0, 1.5	Windows (7+) macOS (10.12+) Linux Android (5.0+) iOS (11.4+) Firefox OS Maemo ESR uniquement pour : Windows (7+) macOS (10.12+) Linux	Activé par défaut [103]	Activé par défaut [103]	Oui [103]	Non	Non	Non	Non	Oui [75]	Non	Non affecté [104]	Pas affecté	Vulnérable	Vulnérable	Pas affecté	Vulnérable	Oui [n 10]
2	Désactivé par défaut [103] [105]	Activé par défaut	Oui	Non	Non	Non	Non	Oui	Oui [76]	Pas affecté	Pas affecté	Vulnérable	Vulnérable	Pas affecté	Vulnérable	Oui [n 10]
3–7	Désactivé par défaut	Activé par défaut	Oui	Non	Non	Non	Oui	Oui	Oui	Pas affecté	Pas affecté	Vulnérable	Vulnérable	Pas affecté	Vulnérable	Oui [n 10]
8–10 RSE 10	Non [105]	Activé par défaut	Oui	Non	Non	Non	Oui	Oui	Oui	Pas affecté	Pas affecté	Vulnérable	Vulnérable	Pas affecté	Vulnérable	Oui [n 10]
11–14	Non	Activé par défaut	Oui	Non	Non	Non	Oui	Oui	Oui	Pas affecté	Vulnérable (SPDY) [85]	Vulnérable	Vulnérable	Pas affecté	Vulnérable	Oui [n 10]
15–22 RSE 17.0–17.0.10	Non	Activé par défaut	Oui	Non	Non	Non	Oui	Oui	Oui	Pas affecté	Atténué	Vulnérable	Vulnérable	Pas affecté	Vulnérable	Oui [n 10]
RSE 17.0.11	Non	Activé par défaut	Oui	Non	Non	Non	Oui	Oui	Oui	Pas affecté	Atténué	Vulnérable	Priorité la plus basse [106] [107]	Pas affecté	Vulnérable	Oui [n 10]
23	Non	Activé par défaut	Oui	Désactivé par défaut [108]	Non	Non	Oui	Oui	Oui	Pas affecté	Atténué	Vulnérable	Vulnérable	Pas affecté	Vulnérable	Oui [n 18]
24, 25.0.0 RSE 24.0–24.1.0	Non	Activé par défaut	Oui	Désactivé par défaut	Désactivé par défaut [109]	Non	Oui	Oui	Oui	Pas affecté	Atténué	Vulnérable	Vulnérable	Pas affecté	Vulnérable	Oui [n 18]
25.0.1, 26 ESR 24.1.1	Non	Activé par défaut	Oui	Désactivé par défaut	Désactivé par défaut	Non	Oui	Oui	Oui	Pas affecté	Atténué	Vulnérable	Priorité la plus basse [106] [107]	Pas affecté	Vulnérable	Oui [n 18]
27–33 RSE 31.0–31.2	Non	Activé par défaut	Oui	Oui [110] [111]	Oui [112] [111]	Non	Oui	Oui	Oui	Pas affecté	Atténué	Vulnérable	Priorité la plus basse	Pas affecté	Vulnérable	Oui [n 18]
34, 35 ESR 31.3–31.7	Non	Désactivé par défaut [113] [114]	Oui	Oui	Oui	Non	Oui	Oui	Oui	Pas affecté	Atténué	Atténué [n 19]	Priorité la plus basse	Pas affecté	Vulnérable	Oui [n 18]
RSE 31.8	Non	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Pas affecté	Atténué	Atténué	Priorité la plus basse	Pas affecté	Atténué [117]	Oui [n 18]
36–38 RSE 38,0	Non	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Pas affecté	Atténué	Atténué	Uniquement comme repli [n 15] [118]	Pas affecté	Vulnérable	Oui [n 18]
RSE 38.1–38.8	Non	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Pas affecté	Atténué	Atténué	Uniquement comme repli [n 15]	Pas affecté	Atténué [117]	Oui [n 18]
39–43	Non	Non [119]	Oui	Oui	Oui	Non	Oui	Oui	Oui	Pas affecté	Atténué	Pas affecté	Uniquement comme repli [n 15]	Pas affecté	Atténué [117]	Oui [n 18]
44–48 RSE 45	Non	Non	Oui	Oui	Oui	Non	Oui	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16] [120] [121] [122] [123]	Pas affecté	Atténué	Oui [n 18]
49–59 RSE 52	Non	Non	Oui	Oui	Oui	Désactivé par défaut (version brouillon) [124]	Oui	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16]	Pas affecté	Atténué	Oui [n 18]
60–62 RSE 60	Non	Non	Oui	Oui	Oui	Oui (version préliminaire)	Oui	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16]	Pas affecté	Atténué	Oui [n 18]
63–77 RSE 68	Non	Non	Oui	Oui	Oui	Oui	Oui	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16]	Pas affecté	Atténué	Oui [n 18]
78–99 RSE 78 RSE 91,0–91,8	Non	Non	Désactivé par défaut [125]	Désactivé par défaut [125]	Oui	Oui	Oui	Oui	Oui	Pas affecté	Atténué	Pas affecté	Désactivé par défaut [n 16]	Pas affecté	Atténué	Oui [n 18]
RSE 91.9	100
Navigateur	Version	Plateformes	SSL 2.0 (non sécurisé)	SSL 3.0 (non sécurisé)	TLS 1.0 (obsolète)	TLS 1.1 (obsolète)	TLS 1.2	TLS 1.3	Certificat VE	Certificat SHA-2	Certificat ECDSA	LA BÊTE	LA CRIMINALITÉ	CANICHE (SSLv3)	RC4	MONSTRE	Embâcle	Sélection du protocole par l’utilisateur
Microsoft Internet Explorer (1–10) [n 20]	1 fois	Windows 3.1 , 95 , NT , [n 21] [n 22] Mac OS 7 , 8	Pas de prise en charge SSL/TLS
2	Oui	Non	Non	Non	Non	Non	Non	Non	Non	Pas de prise en charge SSL 3.0 ou TLS	Vulnérable	Vulnérable	Vulnérable	N / A
3	Oui	Oui [128]	Non	Non	Non	Non	Non	Non	Non	Vulnérable	Pas affecté	Vulnérable	Vulnérable	Vulnérable	Vulnérable	Inconnue
4 , 5 , 6	Windows 3.1 , 95 , 98 , NT , 2000 [n 21] [n 22] Mac OS 7.1 , 8 , X , Solaris , HP-UX	Activé par défaut	Activé par défaut	Désactivé par défaut [128]	Non	Non	Non	Non	Non	Non	Vulnérable	Pas affecté	Vulnérable	Vulnérable	Vulnérable	Vulnérable	Oui [n 10]
6	Windows XP [n 22]	Activé par défaut	Activé par défaut	Désactivé par défaut	Non	Non	Non	Non	Oui (depuis SP3) [n 23] [129]	Non	Atténué	Pas affecté	Vulnérable	Vulnérable	Vulnérable	Vulnérable	Oui [n 10]
7 , 8	Désactivé par défaut [130]	Activé par défaut	Oui [130]	Non	Non	Non	Oui	Oui (depuis SP3) [n 23] [129]	Non	Atténué	Pas affecté	Vulnérable	Vulnérable	Vulnérable	Vulnérable	Oui [n 10]
6	Serveur 2003 [n 22]	Activé par défaut	Activé par défaut	Désactivé par défaut	Non	Non	Non	Non	Oui (KB938397+KB968730) [n 23] [129]	Non	Atténué	Pas affecté	Vulnérable	Vulnérable	Atténué [133]	Atténué [134]	Oui [n 10]
7 , 8	Désactivé par défaut [130]	Activé par défaut	Oui [130]	Non	Non	Non	Oui	Oui (KB938397+KB968730) [n 23] [129]	Non	Atténué	Pas affecté	Vulnérable	Vulnérable	Atténué [133]	Atténué [134]	Oui [n 10]
7 , 8 , 9	Windows Vista	Désactivé par défaut	Activé par défaut	Oui	Non	Non	Non	Oui	Oui	Oui [76]	Atténué	Pas affecté	Vulnérable	Vulnérable	Atténué [133]	Atténué [134]	Oui [n 10]
7 , 8 , 9	Serveur 2008	Désactivé par défaut	Activé par défaut	Oui	Désactivé par défaut [135] (KB4019276)	Désactivé par défaut [135] (KB4019276)	Non	Oui	Oui	Oui [76]	Atténué	Pas affecté	Vulnérable	Vulnérable	Atténué [133]	Atténué [134]	Oui [n 10]
8 , 9 , 10	Windows 7/8 Serveur 2008 R2 / 2012 _	Désactivé par défaut	Activé par défaut	Oui	Désactivé par défaut [136]	Désactivé par défaut [136]	Non	Oui	Oui	Oui	Atténué	Pas affecté	Vulnérable	Priorité la plus basse [137] [n 24]	Atténué [133]	Atténué [134]	Oui [n 10]
Internet Explorer 11 [n 20]	11	Windows 7 Serveur 2008 R2	Désactivé par défaut	Désactivé par défaut [n 25]	Oui	Oui [139]	Oui [139]	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué [n 25]	Désactivé par défaut [143]	Atténué [133]	Atténué [134]	Oui [n 10]
11 [144]	Windows 8.1	Désactivé par défaut	Désactivé par défaut [n 25]	Oui	Oui [139]	Oui [139]	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué [n 25]	Désactivé par défaut [n 16]	Atténué [133]	Atténué [134]	Oui [n 10]
Serveur 2012 Serveur 2012 R2
Navigateur	Version	Plateformes	SSL 2.0 (non sécurisé)	SSL 3.0 (non sécurisé)	TLS 1.0 (obsolète)	TLS 1.1 (obsolète)	TLS 1.2	TLS 1.3	Certificat VE	Certificat SHA-2	Certificat ECDSA	LA BÊTE	LA CRIMINALITÉ	CANICHE (SSLv3)	RC4	MONSTRE	Embâcle	Sélection du protocole par l’utilisateur
Microsoft Edge (12–18) (basé sur EdgeHTML) Client uniquement Internet Explorer 11 [n 20]	11	12–13	Windows 10 1507–1511	Désactivé par défaut	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
11	14–18 (client uniquement)	Windows 10 1607–2004 Windows Serveur (SAC) 1709–2004	Non [145]	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
Internet Explorer 11 [n 20]	11	Windows 10 20H2 Windows Serveur (SAC) 20H2	Non	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
11	Windows 10 21H1	Non	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
11	Windows 10 21H2	Non	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
11	Windows 11	Non	Désactivé par défaut	Oui	Oui	Oui	Oui [146]	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
Internet Explorer 11 [n 20] Versions LTSC	11	Windows 10 LTSB 2015 (1507)	Désactivé par défaut	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
11	Windows 10 LTSB 2016 (1607)	Non [145]	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
11	Windows Server 2016 (LTSB / 1607)	Non [145]	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
11	Windows 10 LTSC 2019 (1809) Windows Server 2019 (LTSC / 1809)	Non	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
11	Windows 10 LTSC 2021 (21H2)	Non	Désactivé par défaut	Oui	Oui	Oui	Non	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
11	Windows Server 2022 (LTSC)	Non	Désactivé par défaut	Oui	Oui	Oui	Oui [146]	Oui	Oui	Oui	Atténué	Pas affecté	Atténué	Désactivé par défaut [n 16]	Atténué	Atténué	Oui [n 10]
Navigateur	Version	Plateformes	SSL 2.0 (non sécurisé)	SSL 3.0 (non sécurisé)	TLS 1.0 (obsolète)	TLS 1.1 (obsolète)	TLS 1.2	TLS 1.3	Certificat VE	Certificat SHA-2	Certificat ECDSA	LA BÊTE	LA CRIMINALITÉ	CANICHE (SSLv3)	RC4	MONSTRE	Embâcle	Sélection du protocole par l’utilisateur
Microsoft Internet Explorer Mobile [n 20]	7, 9	Windows Phone 7, 7.5, 7.8	Disabled by default [130]	Enabled by default	Yes	No [citation needed]	No [citation needed]	No	No [citation needed]	Yes	Yes[147]	Un­known	Not affected	Vulnerable	Vulnerable	Vulnerable	Vulnerable	Only with 3rd party tools[n 26]
10	Windows Phone 8	Disabled by default	Enabled by default	Yes	Disabled by default [149]	Disabled by default [149]	No	No [citation needed]	Yes	Yes[150]	Mitigated	Not affected	Vulnerable	Vulnerable	Vulnerable	Vulnerable	Only with 3rd party tools[n 26]
11	Windows Phone 8.1	Disabled by default	Enabled by default	Yes	Yes[151]	Yes[151]	No	No [citation needed]	Yes	Yes	Mitigated	Not affected	Vulnerable	Only as fallback [n 15][152][153]	Vulnerable	Vulnerable	Only with 3rd party tools[n 26]
Microsoft Edge (13–15) (EdgeHTML-based) [n 27]	13	Windows 10 Mobile 1511	Disabled by default	Disabled by default	Yes	Yes	Yes	No	Yes	Yes	Yes	Mitigated	Not affected	Mitigated	Disabled by default[n 16]	Mitigated	Mitigated	No
14, 15	Windows 10 Mobile 1607–1709	No[145]	Disabled by default	Yes	Yes	Yes	No	Yes	Yes	Yes	Mitigated	Not affected	Mitigated	Disabled by default[n 16]	Mitigated	Mitigated	No
Browser	Version	Platforms	SSL 2.0 (insecure)	SSL 3.0 (insecure)	TLS 1.0 (deprecated)	TLS 1.1 (deprecated)	TLS 1.2	TLS 1.3	EV certificate	SHA-2 certificate	ECDSA certificate	BEAST	CRIME	POODLE (SSLv3)	RC4	FREAK	Logjam	Protocol selection by user
Apple Safari [n 28]	1	Mac OS X 10.2, 10.3	No[158]	Yes	Yes	No	No	No	No	No	No	Vulnerable	Not affected	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
2–5	Mac OS X 10.4, 10.5, Win XP	No	Yes	Yes	No	No	No	since v3.2	No	No	Vulnerable	Not affected	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
3–5	Vista, Win 7	No	Yes	Yes	No	No	No	since v3.2	No	Yes[147]	Vulnerable	Not affected	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
4–6	Mac OS X 10.6, 10.7	No	Yes	Yes	No	No	No	Yes	Yes[75]	Yes[76]	Vulnerable	Not affected	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
6	OS X 10.8	No	Yes	Yes	No	No	No	Yes	Yes	Yes[76]	Mitigated [n 29]	Not affected	Mitigated [n 30]	Vulnerable [n 30]	Mitigated [164]	Vulnerable	No
7, 9	OS X 10.9	No	Yes	Yes	Yes[165]	Yes[165]	No	Yes	Yes	Yes	Mitigated [160]	Not affected	Mitigated [n 30]	Vulnerable [n 30]	Mitigated [164]	Vulnerable	No
8–10	OS X 10.10	No	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Mitigated	Not affected	Mitigated [n 30]	Lowest priority [166][n 30]	Mitigated [164]	Mitigated [167]	No
9–11	OS X 10.11	No	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Lowest priority	Mitigated	Mitigated	No
10–13	macOS 10.12, 10.13	No	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Disabled by default[n 16]	Mitigated	Mitigated	No
12–14	macOS 10.14	No	No	Yes	Yes	Yes	Yes (since macOS 10.14.4)[168]	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Disabled by default[n 16]	Mitigated	Mitigated	No
13, 14	15	macOS 10.15	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Disabled by default[n 16]	Mitigated	Mitigated	No
14	15	macOS 11	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Disabled by default[n 16]	Mitigated	Mitigated	No
15	macOS 12	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Disabled by default[n 16]	Mitigated	Mitigated	No
Browser	Version	Platforms	SSL 2.0 (insecure)	SSL 3.0 (insecure)	TLS 1.0 (deprecated)	TLS 1.1 (deprecated)	TLS 1.2	TLS 1.3	EV certificate	SHA-2 certificate	ECDSA certificate	BEAST	CRIME	POODLE (SSLv3)	RC4	FREAK	Logjam	Protocol selection by user
Apple Safari (mobile) [n 31]	3	iPhone OS 1, 2	No[172]	Yes	Yes	No	No	No	No	No	No	Vulnerable	Not affected	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
4, 5	iPhone OS 3, iOS 4	No	Yes	Yes	No	No	No	Yes[173]	Yes	since iOS 4[147]	Vulnerable	Not affected	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
5, 6	iOS 5, 6	No	Yes	Yes	Yes[169]	Yes[169]	No	Yes	Yes	Yes	Vulnerable	Not affected	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
7	iOS 7	No	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes[174]	Mitigated [175]	Not affected	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
8	iOS 8	No	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Mitigated	Not affected	Mitigated [n 30]	Lowest priority [176][n 30]	Mitigated [177]	Mitigated [178]	No
9	iOS 9	No	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Lowest priority	Mitigated	Mitigated	No
10, 11	iOS 10, 11	No	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Disabled by default[n 16]	Mitigated	Mitigated	No
12	iOS 12	No	No	Yes	Yes	Yes	Yes (since iOS 12.2)[168]	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Disabled by default[n 16]	Mitigated	Mitigated	No
13, 14	iOS 13, 14	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Disabled by default[n 16]	Mitigated	Mitigated	No
iPadOS 13, 14
15	iOS 15	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Mitigated	Not affected	Not affected	Disabled by default[n 16]	Mitigated	Mitigated	No
iPadOS 15
Browser	Version	Platforms	SSL 2.0 (insecure)	SSL 3.0 (insecure)	TLS 1.0 (deprecated)	TLS 1.1 (deprecated)	TLS 1.2	TLS 1.3	EV [n 3]	SHA-2	ECDSA	BEAST[n 4]	CRIME[n 5]	POODLE (SSLv3)[n 6]	RC4[n 7]	FREAK[77][78]	Logjam	Protocol selection by user
Google Android OS [179]	Android 1.0–4.0.4	No	Enabled by default	Yes	No	No	No	Un­known	Yes[75]	since 3.0[147][76]	Un­known	Un­known	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
Android 4.1–4.4.4	No	Enabled by default	Yes	Disabled by default[180]	Disabled by default[180]	No	Un­known	Yes	Yes	Un­known	Un­known	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
Android 5.0–5.0.2	No	Enabled by default	Yes	Yes[180][181]	Yes[180][181]	No	Un­known	Yes	Yes	Un­known	Un­known	Vulnerable	Vulnerable	Vulnerable	Vulnerable	No
Android 5.1–5.1.1	No	Disabled by default [citation needed]	Yes	Yes	Yes	No	Un­known	Yes	Yes	Un­known	Un­known	Not affected	Only as fallback [n 15]	Mitigated	Mitigated	No
Android 6.0–7.1.2	No	Disabled by default [citation needed]	Yes	Yes	Yes	No	Un­known	Yes	Yes	Un­known	Un­known	Not affected	Disabled by default	Mitigated	Mitigated	No
Android 8.0–8.1	No	No [182]	Yes	Yes	Yes	No	Un­known	Yes	Yes	Un­known	Un­known	Not affected	Disabled by default	Mitigated	Mitigated	No
Android 9	No	No	Yes	Yes	Yes	No	Un­known	Yes	Yes	Un­known	Un­known	Not affected	Disabled by default	Mitigated	Mitigated	No
Android 10	No	No	Yes	Yes	Yes	Yes	Un­known	Yes	Yes	Un­known	Un­known	Not affected	Disabled by default	Mitigated	Mitigated	No
Android 11	No	No	Yes	Yes	Yes	Yes	Un­known	Yes	Yes	Un­known	Un­known	Not affected	Disabled by default	Mitigated	Mitigated	No
Android 12 / 12L	No	No	Un­known	Un­known	Yes	Yes	Un­known	Yes	Yes	Un­known	Un­known	Not affected	Disabled by default	Mitigated	Mitigated	No
Android 13	No	No	Un­known	Un­known	Yes	Yes	Un­known	Yes	Yes	Un­known	Un­known	Not affected	Disabled by default	Mitigated	Mitigated	No
Browser	Version	Platforms	SSL 2.0 (insecure)	SSL 3.0 (insecure)	TLS 1.0 (deprecated)	TLS 1.1 (deprecated)	TLS 1.2	TLS 1.3	EV certificate	SHA-2 certificate	ECDSA certificate	BEAST	CRIME	POODLE (SSLv3)	RC4	FREAK	Logjam	Protocol selection by user
Color or Note	Significance
Browser version	Platform
Browser version	Operating system	Future release; under development
Browser version	Operating system	Current latest release
Browser version	Operating system	Former release; still supported
Browser version	Operating system	Former release; long-term support still active, but will end in less than 12 months
Browser version	Operating system	Former release; no longer supported
n/a	Operating system	Mixed / Unspecified
Operating system (Version+)	Minimum required operating system version (for supported versions of the browser)
Operating system	No longer supported for this operating system

Notes

1. ^ Does the browser have mitigations or is not vulnerable for the known attacks. Note actual security depends on other factors such as negotiated cipher, encryption strength, etc. (see § Cipher table).
2. ^ Whether a user or administrator can choose the protocols to be used or not. If yes, several attacks such as BEAST (vulnerable in SSL 3.0 and TLS 1.0) or POODLE (vulnerable in SSL 3.0) can be avoided.
3. ^ ^{a b} Whether EV SSL and DV SSL (normal SSL) can be distinguished by indicators (green lock icon, green address bar, etc.) or not.
4. ^ ^{a b} e.g. 1/n-1 record splitting.
5. ^ ^{a b} e.g. Disabling header compression in HTTPS/SPDY.
6. ^ ^{a b}
   • Complete mitigations; disabling SSL 3.0 itself, “anti-POODLE record splitting”. “Anti-POODLE record splitting” is effective only with client-side implementation and valid according to the SSL 3.0 specification, however, it may also cause compatibility issues due to problems in server-side implementations.
   • Partial mitigations; disabling fallback to SSL 3.0, TLS_FALLBACK_SCSV, disabling cipher suites with CBC mode of operation. If the server also supports TLS_FALLBACK_SCSV, the POODLE attack will fail against this combination of server and browser, but connections where the server does not support TLS_FALLBACK_SCSV and does support SSL 3.0 will still be vulnerable. If disabling cipher suites with CBC mode of operation in SSL 3.0, only cipher suites with RC4 are available, RC4 attacks become easier.
   • When disabling SSL 3.0 manually, POODLE attack will fail.
7. ^ ^{a b}
   • Complete mitigation; disabling cipher suites with RC4.
   • Partial mitigations to keeping compatibility with old systems; setting the priority of RC4 to lower.
8. ^ Google Chrome (and Chromium) supports TLS 1.0, and TLS 1.1 from version 22 (it was added, then dropped from version 21). TLS 1.2 support has been added, then dropped from Chrome 29.^[79][80][81]
9. ^ Uses the TLS implementation provided by BoringSSL for Android, OS X, and Windows^[82] or by NSS for Linux. Google is switching the TLS library used in Chrome to BoringSSL from NSS completely.
10. ^ ^{a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai} configure enabling/disabling of each protocols via setting/option (menu name is dependent on browsers)
11. ^ ^{a b c d e f g h i j k l} configure the maximum and the minimum version of enabling protocols with command-line option
12. ^ TLS_FALLBACK_SCSV is implemented.^[90] Fallback to SSL 3.0 is disabled since version 39.^[91]
13. ^ In addition to TLS_FALLBACK_SCSV and disabling a fallback to SSL 3.0, SSL 3.0 itself is disabled by default.^[91]
14. ^ ^{a b c} configure the minimum version of enabling protocols via chrome://flags^[95] (the maximum version can be configured with command-line option)
15. ^ ^{a b c d e f g} Only when no cipher suites with other than RC4 is available, cipher suites with RC4 will be used as a fallback.
16. ^ ^{a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj} All RC4 cipher suites are disabled by default.
17. ^ Uses the TLS implementation provided by NSS. As of Firefox 22, Firefox supports only TLS 1.0 despite the bundled NSS supporting TLS 1.1. Since Firefox 23, TLS 1.1 can be enabled, but was not enabled by default due to issues. Firefox 24 has TLS 1.2 support disabled by default. TLS 1.1 and TLS 1.2 have been enabled by default in Firefox 27 release.
18. ^ ^{a b c d e f g h i j k l m n} configure the maximum and the minimum version of enabling protocols via about:config
19. ^ SSL 3.0 itself is disabled by default.^[113] In addition, fallback to SSL 3.0 is disabled since version 34,^[115] and TLS_FALLBACK_SCSV is implemented since 35.0 and ESR 31.3.^[113][116]
20. ^ ^{a b c d e f} IE uses the TLS implementation of the Microsoft Windows operating system provided by the SChannel security support provider. TLS 1.1 and 1.2 are disabled by default until IE11.^[126][127]
21. ^ ^{a b} Windows NT 3.1 supports IE 1–2, Windows NT 3.5 supports IE 1–3, Windows NT 3.51 and Windows NT 4.0 supports IE 1–6
22. ^ ^{a b c d} Windows XP as well as Server 2003 and older support only weak ciphers like 3DES and RC4 out of the box.^[131] The weak ciphers of these SChannel version are not only used for IE, but also for other Microsoft products running on this OS, like Office or Windows Update. Only Windows Server 2003 can get a manual update to support AES ciphers by KB948963^[132]
23. ^ ^{a b c d} MS13-095 or MS14-049 for Windows Server 2003, Windows XP x64 and Windows XP SP3 (32-bit)
24. ^ RC4 can be disabled except as a fallback (Only when no cipher suites with other than RC4 is available, cipher suites with RC4 will be used as a fallback.)^[138]
25. ^ ^{a b c d} Fallback to SSL 3.0 is sites blocked by default in Internet Explorer 11 for Protected Mode.^[140][141] SSL 3.0 is disabled by default in Internet Explorer 11 since April 2015.^[142]
26. ^ ^{a b c} Could be disabled via registry editing but need 3rd Party tools to do this.^[148]
27. ^ Edge (formerly known as Project Spartan) is based on a fork of the Internet Explorer 11 rendering engine.
28. ^ Safari uses the operating system implementation on Mac OS X, Windows (XP, Vista, 7)^[154] with unknown version,^[155] Safari 5 is the last version available for Windows. OS X 10.8 on have SecureTransport support for TLS 1.1 and 1.2^[156] Qualys SSL report simulates Safari 5.1.9 connecting with TLS 1.0 not 1.1 or 1.2^[157]
29. ^ In September 2013, Apple implemented BEAST mitigation in OS X 10.8 (Mountain Lion), but it was not turned on by default, resulting in Safari still being theoretically vulnerable to the BEAST attack on that platform.^[159][160] BEAST mitigation has been enabled by default from OS X 10.8.5 updated in February 2014.^[161]
30. ^ ^{a b c d e f g h} Because Apple removed support for all CBC protocols in SSL 3.0 to mitigate POODLE,^[162][163] this leaves only RC4, which is also completely broken by the RC4 attacks in SSL 3.0.
31. ^ Mobile Safari and third-party software utilizing the system UIWebView library use the iOS operating system implementation, which supports TLS 1.2 as of iOS 5.0.^{[169][170][171]}

Libraries

Most SSL and TLS programming libraries are free and open source software.

• BoringSSL, a fork of OpenSSL for Chrome/Chromium and Android as well as other Google applications.
• Botan, a BSD-licensed cryptographic library written in C++.
• BSAFE Micro Edition Suite: a multi-platform implementation of TLS written in C using a FIPS-validated cryptographic module
• BSAFE SSL-J: a TLS library providing both a proprietary API and JSSE API, using FIPS-validated cryptographic module
• cryptlib: a portable open source cryptography library (includes TLS/SSL implementation)
• Delphi programmers may use a library called Indy which utilizes OpenSSL or alternatively ICS which supports TLS 1.3 now.
• GnuTLS: a free implementation (LGPL licensed)
• Java Secure Socket Extension (JSSE): the Java API and provider implementation (named SunJSSE)^[183]
• LibreSSL: a fork of OpenSSL by OpenBSD project.
• MatrixSSL: a dual licensed implementation
• mbed TLS (previously PolarSSL): A tiny SSL library implementation for embedded devices that is designed for ease of use
• Network Security Services: FIPS 140 validated open source library
• OpenSSL: a free implementation (BSD license with some extensions)
• SChannel: an implementation of SSL and TLS Microsoft Windows as part of its package.
• Secure Transport: an implementation of SSL and TLS used in OS X and iOS as part of their packages.
• wolfSSL (previously CyaSSL): Embedded SSL/TLS Library with a strong focus on speed and size.

Library support for TLS/SSL

Implementation	SSL 2.0 (insecure)	SSL 3.0 (insecure)	TLS 1.0	TLS 1.1	TLS 1.2	TLS 1.3
Botan	No	No[184]	Yes	Yes	Yes
BSAFE Micro Edition Suite	No	Disabled by default	Yes	Yes	Yes	In development
BSAFE SSL-J	No	Disabled by default	Yes	Yes	Yes	Yes
cryptlib	No	Disabled by default at compile time	Yes	Yes	Yes
GnuTLS	No[a]	Disabled by default[185]	Yes	Yes	Yes	Yes[186]
JSSE	No[a]	Disabled by default[187]	Disabled by default[188]	Disabled by default[188]	Yes	Yes
LibreSSL	No[189]	No[190]	Yes	Yes	Yes	As of version 3.2.2 [191][192]
MatrixSSL	No	Disabled by default at compile time[193]	Yes	Yes	Yes	yes (draft version)
mbed TLS (previously PolarSSL)	No	Disabled by default[194]	Yes	Yes	Yes
Network Security Services	No[b]	Disabled by default[195]	Yes	Yes[196]	Yes[197]	Yes[198]
OpenSSL	No[199]	Enabled by default	Yes	Yes[200]	Yes[200]	Yes[201]
SChannel XP / 2003[202]	Disabled by default by MSIE 7	Enabled by default	Enabled by default by MSIE 7	No	No	No
SChannel Vista[203]	Disabled by default	Enabled by default	Yes	No	No	No
SChannel 2008[203]	Disabled by default	Enabled by default	Yes	Disabled by default (KB4019276)[135]	Disabled by default (KB4019276)[135]	No
SChannel 7 / 2008 R2[204]	Disabled by default	Disabled by default in MSIE 11	Yes	Enabled by default by MSIE 11	Enabled by default by MSIE 11	No
SChannel 8 / 2012[204]	Disabled by default	Enabled by default	Yes	Disabled by default	Disabled by default	No
SChannel 8.1 / 2012 R2, 10 v1507 & v1511[204]	Disabled by default	Disabled by default in MSIE 11	Yes	Yes	Yes	No
SChannel 10 v1607 / 2016[145]	No	Disabled by default	Yes	Yes	Yes	No
SChannel 10 v1903[205]	No	Disabled by default	Yes	Yes	Yes	No
SChannel 10 v21H1[206]	No	Disabled by default	Yes	Yes	Yes	No
SChannel 11 / 2022[207]	No	Disabled by default	Yes	Yes	Yes	Yes
Secure Transport OS X 10.2–10.8 / iOS 1–4	Yes	Yes	Yes	No	No
Secure Transport OS X 10.9–10.10 / iOS 5–8	No[c]	Yes	Yes	Yes[c]	Yes[c]
Secure Transport OS X 10.11 / iOS 9	No	No[c]	Yes	Yes	Yes
Seed7 TLS/SSL Library	No	Yes	Yes	Yes	Yes
wolfSSL (previously CyaSSL)	No	Disabled by default[208]	Yes	Yes	Yes	Yes[209]
Implementation	SSL 2.0 (insecure)	SSL 3.0 (insecure)	TLS 1.0	TLS 1.1	TLS 1.2	TLS 1.3

1. ^ SSL 2.0 client hello is supported for backward compatibility reasons even though SSL 2.0 is not supported.
2. ^ Server-side implementation of the SSL/TLS protocol still supports processing of received v2-compatible client hello messages. ^[210]
3. ^ Secure Transport: SSL 2.0 was discontinued in OS X 10.8. SSL 3.0 was discontinued in OS X 10.11 and iOS 9. TLS 1.1 and 1.2 are available on iOS 5.0 and later, and OS X 10.9 and later. ^[211]

^[212]

A paper presented at the 2012 ACM conference on computer and communications security^[213] showed that few applications used some of these SSL libraries correctly, leading to vulnerabilities. According to the authors

“the root cause of most of these vulnerabilities is the terrible design of the APIs to the underlying SSL libraries. Instead of expressing high-level security properties of network tunnels such as confidentiality and authentication, these APIs expose low-level details of the SSL protocol to application developers. As a consequence, developers often use SSL APIs incorrectly, misinterpreting and misunderstanding their manifold parameters, options, side effects, and return values.”

Other uses

The Simple Mail Transfer Protocol (SMTP) can also be protected by TLS. These applications use public key certificates to verify the identity of endpoints.

TLS can also be used for tunnelling an entire network stack to create a VPN, which is the case with OpenVPN and OpenConnect. Many vendors have by now married TLS’s encryption and authentication capabilities with authorization. There has also been substantial development since the late 1990s in creating client technology outside of Web-browsers, in order to enable support for client/server applications. Compared to traditional IPsec VPN technologies, TLS has some inherent advantages in firewall and NAT traversal that make it easier to administer for large remote-access populations.

TLS is also a standard method for protecting Session Initiation Protocol (SIP) application signaling. TLS can be used for providing authentication and encryption of the SIP signalling associated with VoIP and other SIP-based applications.^[214]

Security

Attacks against TLS/SSL

Significant attacks against TLS/SSL are listed below.

In February 2015, IETF issued an informational RFC^[215] summarizing the various known attacks against TLS/SSL.

Renegotiation attack

A vulnerability of the renegotiation procedure was discovered in August 2009 that can lead to plaintext injection attacks against SSL 3.0 and all current versions of TLS.^[216] For example, it allows an attacker who can hijack an https connection to splice their own requests into the beginning of the conversation the client has with the web server. The attacker can’t actually decrypt the client–server communication, so it is different from a typical man-in-the-middle attack. A short-term fix is for web servers to stop allowing renegotiation, which typically will not require other changes unless client certificate authentication is used. To fix the vulnerability, a renegotiation indication extension was proposed for TLS. It will require the client and server to include and verify information about previous handshakes in any renegotiation handshakes.^[217] This extension has become a proposed standard and has been assigned the number RFC 5746. The RFC has been implemented by several libraries.^{[218][219][220]}

Downgrade attacks: FREAK attack and Logjam attack

A protocol downgrade attack (also called a version rollback attack) tricks a web server into negotiating connections with previous versions of TLS (such as SSLv2) that have long since been abandoned as insecure.

Previous modifications to the original protocols, like False Start^[221] (adopted and enabled by Google Chrome^[222]) or Snap Start, reportedly introduced limited TLS protocol downgrade attacks^[223] or allowed modifications to the cipher suite list sent by the client to the server. In doing so, an attacker might succeed in influencing the cipher suite selection in an attempt to downgrade the cipher suite negotiated to use either a weaker symmetric encryption algorithm or a weaker key exchange.^[224] A paper presented at an ACM conference on computer and communications security in 2012 demonstrated that the False Start extension was at risk: in certain circumstances it could allow an attacker to recover the encryption keys offline and to access the encrypted data.^[225]

Encryption downgrade attacks can force servers and clients to negotiate a connection using cryptographically weak keys. In 2014, a man-in-the-middle attack called FREAK was discovered affecting the OpenSSL stack, the default Android web browser, and some Safari browsers.^[226] The attack involved tricking servers into negotiating a TLS connection using cryptographically weak 512 bit encryption keys.

Logjam is a security exploit discovered in May 2015 that exploits the option of using legacy “export-grade” 512-bit Diffie–Hellman groups dating back to the 1990s.^[227] It forces susceptible servers to downgrade to cryptographically weak 512-bit Diffie–Hellman groups. An attacker can then deduce the keys the client and server determine using the Diffie–Hellman key exchange.

Cross-protocol attacks: DROWN

The DROWN attack is an exploit that attacks servers supporting contemporary SSL/TLS protocol suites by exploiting their support for the obsolete, insecure, SSLv2 protocol to leverage an attack on connections using up-to-date protocols that would otherwise be secure.^[228][229] DROWN exploits a vulnerability in the protocols used and the configuration of the server, rather than any specific implementation error. Full details of DROWN were announced in March 2016, together with a patch for the exploit. At that time, more than 81,000 of the top 1 million most popular websites were among the TLS protected websites that were vulnerable to the DROWN attack.^[229]

BEAST attack

On September 23, 2011 researchers Thai Duong and Juliano Rizzo demonstrated a proof of concept called BEAST (Browser Exploit Against SSL/TLS)^[230] using a Java applet to violate same origin policy constraints, for a long-known cipher block chaining (CBC) vulnerability in TLS 1.0:^[231][232] an attacker observing 2 consecutive ciphertext blocks C0, C1 can test if the plaintext block P1 is equal to x by choosing the next plaintext block P2 = x ⊕ {displaystyle oplus } C0 ⊕ {displaystyle oplus } C1; as per CBC operation, C2 = E(C1 ⊕ {displaystyle oplus } P2) = E(C1 ⊕ {displaystyle oplus } x ⊕ {displaystyle oplus } C0 ⊕ {displaystyle oplus } C1) = E(C0 ⊕ {displaystyle oplus } x), which will be equal to C1 if x = P1. Practical exploits had not been previously demonstrated for this vulnerability, which was originally discovered by Phillip Rogaway^[233] in 2002. The vulnerability of the attack had been fixed with TLS 1.1 in 2006, but TLS 1.1 had not seen wide adoption prior to this attack demonstration.

RC4 as a stream cipher is immune to BEAST attack. Therefore, RC4 was widely used as a way to mitigate BEAST attack on the server side. However, in 2013, researchers found more weaknesses in RC4. Thereafter enabling RC4 on server side was no longer recommended.^[234]

Chrome and Firefox themselves are not vulnerable to BEAST attack,^[83][104] however, Mozilla updated their NSS libraries to mitigate BEAST-like attacks. NSS is used by Mozilla Firefox and Google Chrome to implement SSL. Some web servers that have a broken implementation of the SSL specification may stop working as a result.^[235]

Microsoft released Security Bulletin MS12-006 on January 10, 2012, which fixed the BEAST vulnerability by changing the way that the Windows Secure Channel (SChannel) component transmits encrypted network packets from the server end.^[236] Users of Internet Explorer (prior to version 11) that run on older versions of Windows (Windows 7, Windows 8 and Windows Server 2008 R2) can restrict use of TLS to 1.1 or higher.

Apple fixed BEAST vulnerability by implementing 1/n-1 split and turning it on by default in OS X Mavericks, released on October 22, 2013.^[237]

CRIME and BREACH attacks

The authors of the BEAST attack are also the creators of the later CRIME attack, which can allow an attacker to recover the content of web cookies when data compression is used along with TLS.^[238][239] When used to recover the content of secret authentication cookies, it allows an attacker to perform session hijacking on an authenticated web session.

While the CRIME attack was presented as a general attack that could work effectively against a large number of protocols, including but not limited to TLS, and application-layer protocols such as SPDY or HTTP, only exploits against TLS and SPDY were demonstrated and largely mitigated in browsers and servers. The CRIME exploit against HTTP compression has not been mitigated at all, even though the authors of CRIME have warned that this vulnerability might be even more widespread than SPDY and TLS compression combined. In 2013 a new instance of the CRIME attack against HTTP compression, dubbed BREACH, was announced. Based on the CRIME attack a BREACH attack can extract login tokens, email addresses or other sensitive information from TLS encrypted web traffic in as little as 30 seconds (depending on the number of bytes to be extracted), provided the attacker tricks the victim into visiting a malicious web link or is able to inject content into valid pages the user is visiting (ex: a wireless network under the control of the attacker).^[240] All versions of TLS and SSL are at risk from BREACH regardless of the encryption algorithm or cipher used.^[241] Unlike previous instances of CRIME, which can be successfully defended against by turning off TLS compression or SPDY header compression, BREACH exploits HTTP compression which cannot realistically be turned off, as virtually all web servers rely upon it to improve data transmission speeds for users.^[240] This is a known limitation of TLS as it is susceptible to chosen-plaintext attack against the application-layer data it was meant to protect.

Timing attacks on padding

Earlier TLS versions were vulnerable against the padding oracle attack discovered in 2002. A novel variant, called the Lucky Thirteen attack, was published in 2013.

Some experts^[66] also recommended avoiding Triple-DES CBC. Since the last supported ciphers developed to support any program using Windows XP’s SSL/TLS library like Internet Explorer on Windows XP are RC4 and Triple-DES, and since RC4 is now deprecated (see discussion of RC4 attacks), this makes it difficult to support any version of SSL for any program using this library on XP.

A fix was released as the Encrypt-then-MAC extension to the TLS specification, released as RFC 7366.^[242] The Lucky Thirteen attack can be mitigated in TLS 1.2 by using only AES_GCM ciphers; AES_CBC remains vulnerable.^{[citation needed]}

POODLE attack

On October 14, 2014, Google researchers published a vulnerability in the design of SSL 3.0, which makes CBC mode of operation with SSL 3.0 vulnerable to a padding attack (CVE- 2014-3566). They named this attack POODLE (Padding Oracle On Downgraded Legacy Encryption). On average, attackers only need to make 256 SSL 3.0 requests to reveal one byte of encrypted messages.^[73]

Although this vulnerability only exists in SSL 3.0 and most clients and servers support TLS 1.0 and above, all major browsers voluntarily downgrade to SSL 3.0 if the handshakes with newer versions of TLS fail unless they provide the option for a user or administrator to disable SSL 3.0 and the user or administrator does so^{[citation needed]}. Therefore, the man-in-the-middle can first conduct a version rollback attack and then exploit this vulnerability.^[73]

On December 8, 2014, a variant of POODLE was announced that impacts TLS implementations that do not properly enforce padding byte requirements.^[243]

RC4 attacks

Despite the existence of attacks on RC4 that broke its security, cipher suites in SSL and TLS that were based on RC4 were still considered secure prior to 2013 based on the way in which they were used in SSL and TLS. In 2011, the RC4 suite was actually recommended as a work around for the BEAST attack.^[244] New forms of attack disclosed in March 2013 conclusively demonstrated the feasibility of breaking RC4 in TLS, suggesting it was not a good workaround for BEAST.^[72] An attack scenario was proposed by AlFardan, Bernstein, Paterson, Poettering and Schuldt that used newly discovered statistical biases in the RC4 key table^[245] to recover parts of the plaintext with a large number of TLS encryptions.^[246][247] An attack on RC4 in TLS and SSL that requires 13 × 2²⁰ encryptions to break RC4 was unveiled on 8 July 2013 and later described as “feasible” in the accompanying presentation at a USENIX Security Symposium in August 2013.^[248][249] In July 2015, subsequent improvements in the attack make it increasingly practical to defeat the security of RC4-encrypted TLS.^[250]

As many modern browsers have been designed to defeat BEAST attacks (except Safari for Mac OS X 10.7 or earlier, for iOS 6 or earlier, and for Windows; see § Web browsers), RC4 is no longer a good choice for TLS 1.0. The CBC ciphers which were affected by the BEAST attack in the past have become a more popular choice for protection.^[66] Mozilla and Microsoft recommend disabling RC4 where possible.^[251][252] RFC 7465 prohibits the use of RC4 cipher suites in all versions of TLS.

On September 1, 2015, Microsoft, Google and Mozilla announced that RC4 cipher suites would be disabled by default in their browsers (Microsoft Edge, Internet Explorer 11 on Windows 7/8.1/10, Firefox, and Chrome) in early 2016.^{[253][254][255]}

Truncation attack

A TLS (logout) truncation attack blocks a victim’s account logout requests so that the user unknowingly remains logged into a web service. When the request to sign out is sent, the attacker injects an unencrypted TCP FIN message (no more data from sender) to close the connection. The server therefore doesn’t receive the logout request and is unaware of the abnormal termination.^[256]

Published in July 2013,^[257][258] the attack causes web services such as Gmail and Hotmail to display a page that informs the user that they have successfully signed-out, while ensuring that the user’s browser maintains authorization with the service, allowing an attacker with subsequent access to the browser to access and take over control of the user’s logged-in account. The attack does not rely on installing malware on the victim’s computer; attackers need only place themselves between the victim and the web server (e.g., by setting up a rogue wireless hotspot).^[256] This vulnerability also requires access to the victim’s computer. Another possibility is when using FTP the data connection can have a false FIN in the data stream, and if the protocol rules for exchanging close_notify alerts is not adhered to a file can be truncated.

Unholy PAC attack

This attack, discovered in mid-2016, exploits weaknesses in the Web Proxy Autodiscovery Protocol (WPAD) to expose the URL that a web user is attempting to reach via a TLS-enabled web link.^[259] Disclosure of a URL can violate a user’s privacy, not only because of the website accessed, but also because URLs are sometimes used to authenticate users. Document sharing services, such as those offered by Google and Dropbox, also work by sending a user a security token that’s included in the URL. An attacker who obtains such URLs may be able to gain full access to a victim’s account or data.

The exploit works against almost all browsers and operating systems.

Sweet32 attack

The Sweet32 attack breaks all 64-bit block ciphers used in CBC mode as used in TLS by exploiting a birthday attack and either a man-in-the-middle attack or injection of a malicious JavaScript into a web page. The purpose of the man-in-the-middle attack or the JavaScript injection is to allow the attacker to capture enough traffic to mount a birthday attack.^[260]

Implementation errors: Heartbleed bug, BERserk attack, Cloudflare bug

The Heartbleed bug is a serious vulnerability specific to the implementation of SSL/TLS in the popular OpenSSL cryptographic software library, affecting versions 1.0.1 to 1.0.1f. This weakness, reported in April 2014, allows attackers to steal private keys from servers that should normally be protected.^[261] The Heartbleed bug allows anyone on the Internet to read the memory of the systems protected by the vulnerable versions of the OpenSSL software. This compromises the secret private keys associated with the public certificates used to identify the service providers and to encrypt the traffic, the names and passwords of the users and the actual content. This allows attackers to eavesdrop on communications, steal data directly from the services and users and to impersonate services and users.^[262] The vulnerability is caused by a buffer over-read bug in the OpenSSL software, rather than a defect in the SSL or TLS protocol specification.

In September 2014, a variant of Daniel Bleichenbacher’s PKCS#1 v1.5 RSA Signature Forgery vulnerability^[263] was announced by Intel Security Advanced Threat Research. This attack, dubbed BERserk, is a result of incomplete ASN.1 length decoding of public key signatures in some SSL implementations, and allows a man-in-the-middle attack by forging a public key signature.^[264]

In February 2015, after media reported the hidden pre-installation of Superfish adware on some Lenovo notebooks,^[265] a researcher found a trusted root certificate on affected Lenovo machines to be insecure, as the keys could easily be accessed using the company name, Komodia, as a passphrase.^[266] The Komodia library was designed to intercept client-side TLS/SSL traffic for parental control and surveillance, but it was also used in numerous adware programs, including Superfish, that were often surreptitiously installed unbeknownst to the computer user. In turn, these potentially unwanted programs installed the corrupt root certificate, allowing attackers to completely control web traffic and confirm false websites as authentic.

In May 2016, it was reported that dozens of Danish HTTPS-protected websites belonging to Visa Inc. were vulnerable to attacks allowing hackers to inject malicious code and forged content into the browsers of visitors.^[267] The attacks worked because the TLS implementation used on the affected servers incorrectly reused random numbers (nonces) that are intended to be used only once, ensuring that each TLS handshake is unique.^[267]

In February 2017, an implementation error caused by a single mistyped character in code used to parse HTML created a buffer overflow error on Cloudflare servers. Similar in its effects to the Heartbleed bug discovered in 2014, this overflow error, widely known as Cloudbleed, allowed unauthorized third parties to read data in the memory of programs running on the servers—data that should otherwise have been protected by TLS.^[268]

Survey of websites vulnerable to attacks

As of July 2021^[update], the Trustworthy Internet Movement estimated the ratio of websites that are vulnerable to TLS attacks.^[71]

Survey of the TLS vulnerabilities of the most popular websites

Attacks	Security
Insecure	Depends	Secure	Other
Renegotiation attack	0.1% support insecure renegotiation	<0.1% support both	99.2% support secure renegotiation	0.7% no support
RC4 attacks	0.4% support RC4 suites used with modern browsers	6.5% support some RC4 suites	93.1% no support	N/A
TLS Compression (CRIME attack)	>0.0% vulnerable	N/A	N/A	N/A
Heartbleed	>0.0% vulnerable	N/A	N/A	N/A
ChangeCipherSpec injection attack	0.1% vulnerable and exploitable	0.2% vulnerable, not exploitable	98.5% not vulnerable	1.2% unknown
POODLE attack against TLS (Original POODLE against SSL 3.0 is not included)	0.1% vulnerable and exploitable	0.1% vulnerable, not exploitable	99.8% not vulnerable	0.2% unknown
Protocol downgrade	6.6% Downgrade defence not supported	N/A	72.3% Downgrade defence supported	21.0% unknown

Forward secrecy

Forward secrecy is a property of cryptographic systems which ensures that a session key derived from a set of public and private keys will not be compromised if one of the private keys is compromised in the future.^[269] Without forward secrecy, if the server’s private key is compromised, not only will all future TLS-encrypted sessions using that server certificate be compromised, but also any past sessions that used it as well (provided of course that these past sessions were intercepted and stored at the time of transmission).^[270] An implementation of TLS can provide forward secrecy by requiring the use of ephemeral Diffie–Hellman key exchange to establish session keys, and some notable TLS implementations do so exclusively: e.g., Gmail and other Google HTTPS services that use OpenSSL.^[271] However, many clients and servers supporting TLS (including browsers and web servers) are not configured to implement such restrictions.^[272][273] In practice, unless a web service uses Diffie–Hellman key exchange to implement forward secrecy, all of the encrypted web traffic to and from that service can be decrypted by a third party if it obtains the server’s master (private) key; e.g., by means of a court order.^[274]

Even where Diffie–Hellman key exchange is implemented, server-side session management mechanisms can impact forward secrecy. The use of TLS session tickets (a TLS extension) causes the session to be protected by AES128-CBC-SHA256 regardless of any other negotiated TLS parameters, including forward secrecy ciphersuites, and the long-lived TLS session ticket keys defeat the attempt to implement forward secrecy.^{[275][276][277]} Stanford University research in 2014 also found that of 473,802 TLS servers surveyed, 82.9% of the servers deploying ephemeral Diffie–Hellman (DHE) key exchange to support forward secrecy were using weak Diffie–Hellman parameters. These weak parameter choices could potentially compromise the effectiveness of the forward secrecy that the servers sought to provide.^[278]

Since late 2011, Google has provided forward secrecy with TLS by default to users of its Gmail service, along with Google Docs and encrypted search, among other services.^[279] Since November 2013, Twitter has provided forward secrecy with TLS to users of its service.^[280] As of August 2019^[update], about 80% of TLS-enabled websites are configured to use cipher suites that provide forward secrecy to most web browsers.^[71]

TLS interception

TLS interception (or HTTPS interception if applied particularly to that protocol) is the practice of intercepting an encrypted data stream in order to decrypt it, read and possibly manipulate it, and then re-encrypt it and send the data on its way again. This is done by way of a “transparent proxy”: the interception software terminates the incoming TLS connection, inspects the HTTP plaintext, and then creates a new TLS connection to the destination.^[281]

TLS / HTTPS interception is used as an information security measure by network operators in order to be able to scan for and protect against the intrusion of malicious content into the network, such as computer viruses and other malware.^[281] Such content could otherwise not be detected as long as it is protected by encryption, which is increasingly the case as a result of the routine use of HTTPS and other secure protocols.

A significant drawback of TLS / HTTPS interception is that it introduces new security risks of its own. One notable limitation is that it provides a point where network traffic is available unencrypted thus giving attackers an incentive to attack this point in particular in order to gain access to otherwise secure content. The interception also allows the network operator, or persons who gain access to its interception system, to perform man-in-the-middle attacks against network users. A 2017 study found that “HTTPS interception has become startlingly widespread, and that interception products as a class have a dramatically negative impact on connection security”.^[281]

Protocol details

The TLS protocol exchanges records, which encapsulate the data to be exchanged in a specific format (see below). Each record can be compressed, padded, appended with a message authentication code (MAC), or encrypted, all depending on the state of the connection. Each record has a content type field that designates the type of data encapsulated, a length field and a TLS version field. The data encapsulated may be control or procedural messages of the TLS itself, or simply the application data needed to be transferred by TLS. The specifications (cipher suite, keys etc.) required to exchange application data by TLS, are agreed upon in the “TLS handshake” between the client requesting the data and the server responding to requests. The protocol therefore defines both the structure of payloads transferred in TLS and the procedure to establish and monitor the transfer.

TLS handshake

Simplified illustration of the full TLS 1.2 handshake with timing information.

When the connection starts, the record encapsulates a “control” protocol – the handshake messaging protocol (content type 22). This protocol is used to exchange all the information required by both sides for the exchange of the actual application data by TLS. It defines the format of messages and the order of their exchange. These may vary according to the demands of the client and server – i.e., there are several possible procedures to set up the connection. This initial exchange results in a successful TLS connection (both parties ready to transfer application data with TLS) or an alert message (as specified below).

Basic TLS handshake

A typical connection example follows, illustrating a handshake where the server (but not the client) is authenticated by its certificate:

1. Negotiation phase:
   • A client sends a ClientHello message specifying the highest TLS protocol version it supports, a random number, a list of suggested cipher suites and suggested compression methods. If the client is attempting to perform a resumed handshake, it may send a session ID. If the client can use Application-Layer Protocol Negotiation, it may include a list of supported application protocols, such as HTTP/2.
   • The server responds with a ServerHello message, containing the chosen protocol version, a random number, cipher suite and compression method from the choices offered by the client. To confirm or allow resumed handshakes the server may send a session ID. The chosen protocol version should be the highest that both the client and server support. For example, if the client supports TLS version 1.1 and the server supports version 1.2, version 1.1 should be selected; version 1.2 should not be selected.
   • The server sends its Certificate message (depending on the selected cipher suite, this may be omitted by the server).^[282]
   • The server sends its ServerKeyExchange message (depending on the selected cipher suite, this may be omitted by the server). This message is sent for all DHE, ECDHE and DH_anon cipher suites.^[7]
   • The server sends a ServerHelloDone message, indicating it is done with handshake negotiation.
   • The client responds with a ClientKeyExchange message, which may contain a PreMasterSecret, public key, or nothing. (Again, this depends on the selected cipher.) This PreMasterSecret is encrypted using the public key of the server certificate.
   • The client and server then use the random numbers and PreMasterSecret to compute a common secret, called the “master secret”. All other key data (session keys such as IV, symmetric encryption key, MAC key^[283]) for this connection is derived from this master secret (and the client- and server-generated random values), which is passed through a carefully designed pseudorandom function.
2. The client now sends a ChangeCipherSpec record, essentially telling the server, “Everything I tell you from now on will be authenticated (and encrypted if encryption parameters were present in the server certificate).” The ChangeCipherSpec is itself a record-level protocol with content type of 20.
   • The client sends an authenticated and encrypted Finished message, containing a hash and MAC over the previous handshake messages.
   • The server will attempt to decrypt the client’s Finished message and verify the hash and MAC. If the decryption or verification fails, the handshake is considered to have failed and the connection should be torn down.
3. Finally, the server sends a ChangeCipherSpec, telling the client, “Everything I tell you from now on will be authenticated (and encrypted, if encryption was negotiated).”
   • The server sends its authenticated and encrypted Finished message.
   • The client performs the same decryption and verification procedure as the server did in the previous step.
4. Application phase: at this point, the “handshake” is complete and the application protocol is enabled, with content type of 23. Application messages exchanged between client and server will also be authenticated and optionally encrypted exactly like in their Finished message. Otherwise, the content type will return 25 and the client will not authenticate.

Client-authenticated TLS handshake

The following full example shows a client being authenticated (in addition to the server as in the example above; see mutual authentication) via TLS using certificates exchanged between both peers.

1. Negotiation Phase:
   • A client sends a ClientHello message specifying the highest TLS protocol version it supports, a random number, a list of suggested cipher suites and compression methods.
   • The server responds with a ServerHello message, containing the chosen protocol version, a random number, cipher suite and compression method from the choices offered by the client. The server may also send a session id as part of the message to perform a resumed handshake.
   • The server sends its Certificate message (depending on the selected cipher suite, this may be omitted by the server).^[282]
   • The server sends its ServerKeyExchange message (depending on the selected cipher suite, this may be omitted by the server). This message is sent for all DHE, ECDHE and DH_anon ciphersuites.^[7]
   • The server sends a CertificateRequest message, to request a certificate from the client.
   • The server sends a ServerHelloDone message, indicating it is done with handshake negotiation.
   • The client responds with a Certificate message, which contains the client’s certificate, but not it’s private key.
   • The client sends a ClientKeyExchange message, which may contain a PreMasterSecret, public key, or nothing. (Again, this depends on the selected cipher.) This PreMasterSecret is encrypted using the public key of the server certificate.
   • The client sends a CertificateVerify message, which is a signature over the previous handshake messages using the client’s certificate’s private key. This signature can be verified by using the client’s certificate’s public key. This lets the server know that the client has access to the private key of the certificate and thus owns the certificate.
   • The client and server then use the random numbers and PreMasterSecret to compute a common secret, called the “master secret”. All other key data (“session keys”) for this connection is derived from this master secret (and the client- and server-generated random values), which is passed through a carefully designed pseudorandom function.
2. The client now sends a ChangeCipherSpec record, essentially telling the server, “Everything I tell you from now on will be authenticated (and encrypted if encryption was negotiated). ” The ChangeCipherSpec is itself a record-level protocol and has type 20 and not 22.
   • Finally, the client sends an encrypted Finished message, containing a hash and MAC over the previous handshake messages.
   • The server will attempt to decrypt the client’s Finished message and verify the hash and MAC. If the decryption or verification fails, the handshake is considered to have failed and the connection should be torn down.
3. Finally, the server sends a ChangeCipherSpec, telling the client, “Everything I tell you from now on will be authenticated (and encrypted if encryption was negotiated). ”
   • The server sends its own encrypted Finished message.
   • The client performs the same decryption and verification procedure as the server did in the previous step.
4. Application phase: at this point, the “handshake” is complete and the application protocol is enabled, with content type of 23. Application messages exchanged between client and server will also be encrypted exactly like in their Finished message.

Resumed TLS handshake

Public key operations (e.g., RSA) are relatively expensive in terms of computational power. TLS provides a secure shortcut in the handshake mechanism to avoid these operations: resumed sessions. Resumed sessions are implemented using session IDs or session tickets.

Apart from the performance benefit, resumed sessions can also be used for single sign-on, as it guarantees that both the original session and any resumed session originate from the same client. This is of particular importance for the FTP over TLS/SSL protocol, which would otherwise suffer from a man-in-the-middle attack in which an attacker could intercept the contents of the secondary data connections.^[284]

TLS 1.3 handshake

The TLS 1.3 handshake was condensed to only one round trip compared to the two round trips required in previous versions of TLS/SSL.

First the client sends a clientHello message to the server that contains a list of supported ciphers in order of the client’s preference and makes a guess on what key algorithm will be used so that it can send a secret key to share if needed. By making a guess at what key algorithm will be used, the server eliminates a round trip. After receiving the clientHello, the server sends a serverHello with its key, a certificate, the chosen cipher suite and the finished message.

After the client receives the server’s finished message, it now is coordinated with the server on which cipher suite to use.^[285]

Session IDs

In an ordinary full handshake, the server sends a session id as part of the ServerHello message. The client associates this session id with the server’s IP address and TCP port, so that when the client connects again to that server, it can use the session id to shortcut the handshake. In the server, the session id maps to the cryptographic parameters previously negotiated, specifically the “master secret”. Both sides must have the same “master secret” or the resumed handshake will fail (this prevents an eavesdropper from using a session id). The random data in the ClientHello and ServerHello messages virtually guarantee that the generated connection keys will be different from in the previous connection. In the RFCs, this type of handshake is called an abbreviated handshake. It is also described in the literature as a restart handshake.

1. Negotiation phase:
   • A client sends a ClientHello message specifying the highest TLS protocol version it supports, a random number, a list of suggested cipher suites and compression methods. Included in the message is the session id from the previous TLS connection.
   • The server responds with a ServerHello message, containing the chosen protocol version, a random number, cipher suite and compression method from the choices offered by the client. If the server recognizes the session id sent by the client, it responds with the same session id. The client uses this to recognize that a resumed handshake is being performed. If the server does not recognize the session id sent by the client, it sends a different value for its session id. This tells the client that a resumed handshake will not be performed. At this point, both the client and server have the “master secret” and random data to generate the key data to be used for this connection.
2. The server now sends a ChangeCipherSpec record, essentially telling the client, “Everything I tell you from now on will be encrypted.” The ChangeCipherSpec is itself a record-level protocol and has type 20 and not 22.
   • Finally, the server sends an encrypted Finished message, containing a hash and MAC over the previous handshake messages.
   • The client will attempt to decrypt the server’s Finished message and verify the hash and MAC. If the decryption or verification fails, the handshake is considered to have failed and the connection should be torn down.
3. Finally, the client sends a ChangeCipherSpec, telling the server, “Everything I tell you from now on will be encrypted. ”
   • The client sends its own encrypted Finished message.
   • The server performs the same decryption and verification procedure as the client did in the previous step.
4. Application phase: at this point, the “handshake” is complete and the application protocol is enabled, with content type of 23. Application messages exchanged between client and server will also be encrypted exactly like in their Finished message.

Session tickets

RFC 5077 extends TLS via use of session tickets, instead of session IDs. It defines a way to resume a TLS session without requiring that session-specific state is stored at the TLS server.

When using session tickets, the TLS server stores its session-specific state in a session ticket and sends the session ticket to the TLS client for storing. The client resumes a TLS session by sending the session ticket to the server, and the server resumes the TLS session according to the session-specific state in the ticket. The session ticket is encrypted and authenticated by the server, and the server verifies its validity before using its contents.

One particular weakness of this method with OpenSSL is that it always limits encryption and authentication security of the transmitted TLS session ticket to AES128-CBC-SHA256, no matter what other TLS parameters were negotiated for the actual TLS session.^[276] This means that the state information (the TLS session ticket) is not as well protected as the TLS session itself. Of particular concern is OpenSSL’s storage of the keys in an application-wide context (SSL_CTX), i.e. for the life of the application, and not allowing for re-keying of the AES128-CBC-SHA256 TLS session tickets without resetting the application-wide OpenSSL context (which is uncommon, error-prone and often requires manual administrative intervention).^[277][275]

TLS record

This is the general format of all TLS records.

TLS record format, general

Offset	Byte +0	Byte +1	Byte +2	Byte +3
Byte 0	Content type	N/A
Bytes 1..4	Legacy version	Length
(Major)	(Minor)	(bits 15..8)	(bits 7..0)
Bytes 5..(m−1)	Protocol message(s)
Bytes m..(p−1)	MAC (optional)
Bytes p..(q−1)	Padding (block ciphers only)

Content type This field identifies the Record Layer Protocol Type contained in this record.

Content types

Hex	Dec	Type
0x14	20	ChangeCipherSpec
0x15	21	Alert
0x16	22	Handshake
0x17	23	Application
0x18	24	Heartbeat

Legacy version This field identifies the major and minor version of TLS prior to TLS 1.3 for the contained message. For a ClientHello message, this need not be the highest version supported by the client. For TLS 1.3 and later, this must to be set 0x0303 and application must send supported versions in an extra message extension block.

Versions

Major version	Minor version	Version type
3	0	SSL 3.0
3	1	TLS 1.0
3	2	TLS 1.1
3	3	TLS 1.2
3	4	TLS 1.3

Length The length of “protocol message(s)”, “MAC” and “padding” fields combined (i.e. q−5), not to exceed 2 ¹⁴ bytes (16 KiB). Protocol message(s) One or more messages identified by the Protocol field. Note that this field may be encrypted depending on the state of the connection. MAC and padding A message authentication code computed over the “protocol message(s)” field, with additional key material included. Note that this field may be encrypted, or not included entirely, depending on the state of the connection. No “MAC” or “padding” fields can be present at end of TLS records before all cipher algorithms and parameters have been negotiated and handshaked and then confirmed by sending a CipherStateChange record (see below) for signalling that these parameters will take effect in all further records sent by the same peer. Handshake protocol

Most messages exchanged during the setup of the TLS session are based on this record, unless an error or warning occurs and needs to be signaled by an Alert protocol record (see below), or the encryption mode of the session is modified by another record (see ChangeCipherSpec protocol below).

TLS record format for handshake protocol

Offset	Byte +0	Byte +1	Byte +2	Byte +3
Byte 0	22	N/A
Bytes 1..4	Legacy version	Length
(Major)	(Minor)	(bits 15..8)	(bits 7..0)
Bytes 5..8	Message type	Handshake message data length
(bits 23..16)	(bits 15..8)	(bits 7..0)
Bytes 9..(n−1)	Handshake message data
Bytes n..(n+3)	Message type	Handshake message data length
(bits 23..16)	(bits 15..8)	(bits 7..0)
Bytes (n+4)..	Handshake message data

Message type This field identifies the handshake message type.

Message types

Code	Description
0	HelloRequest
1	ClientHello
2	ServerHello
4	NewSessionTicket
8	EncryptedExtensions (TLS 1.3 only)
11	Certificate
12	ServerKeyExchange
13	CertificateRequest
14	ServerHelloDone
15	CertificateVerify
16	ClientKeyExchange
20	Finished

Handshake message data length This is a 3-byte field indicating the length of the handshake data, not including the header.

Note that multiple handshake messages may be combined within one record.

Alert protocol

This record should normally not be sent during normal handshaking or application exchanges. However, this message can be sent at any time during the handshake and up to the closure of the session. If this is used to signal a fatal error, the session will be closed immediately after sending this record, so this record is used to give a reason for this closure. If the alert level is flagged as a warning, the remote can decide to close the session if it decides that the session is not reliable enough for its needs (before doing so, the remote may also send its own signal).

TLS record format for alert protocol

Offset	Byte +0	Byte +1	Byte +2	Byte +3
Byte 0	21	N/A
Bytes 1..4	Legacy version	Length
(Major)	(Minor)	0	2
Bytes 5..6	Level	Description	N/A
Bytes 7..(p−1)	MAC (optional)
Bytes p..(q−1)	Padding (block ciphers only)

Level This field identifies the level of alert. If the level is fatal, the sender should close the session immediately. Otherwise, the recipient may decide to terminate the session itself, by sending its own fatal alert and closing the session itself immediately after sending it. The use of Alert records is optional, however if it is missing before the session closure, the session may be resumed automatically (with its handshakes). Normal closure of a session after termination of the transported application should preferably be alerted with at least the Close notify Alert type (with a simple warning level) to prevent such automatic resume of a new session. Signalling explicitly the normal closure of a secure session before effectively closing its transport layer is useful to prevent or detect attacks (like attempts to truncate the securely transported data, if it intrinsically does not have a predetermined length or duration that the recipient of the secured data may expect).

Alert level types

Code	Level type	Connection state
1	warning	connection or security may be unstable.
2	fatal	connection or security may be compromised, or an unrecoverable error has occurred.

Description This field identifies which type of alert is being sent.

Alert description types

Code	Description	Level types	Note
0	Close notify	warning/fatal
10	Unexpected message	fatal
20	Bad record MAC	fatal	Possibly a bad SSL implementation, or payload has been tampered with e.g. FTP firewall rule on FTPS server.
21	Decryption failed	fatal	TLS only, reserved
22	Record overflow	fatal	TLS only
30	Decompression failure	fatal
40	Handshake failure	fatal
41	No certificate	warning/fatal	SSL 3.0 only, reserved
42	Bad certificate	warning/fatal
43	Unsupported certificate	warning/fatal	e.g. certificate has only server authentication usage enabled and is presented as a client certificate
44	Certificate revoked	warning/fatal
45	Certificate expired	warning/fatal	Check server certificate expire also check no certificate in the chain presented has expired
46	Certificate unknown	warning/fatal
47	Illegal parameter	fatal
48	Unknown CA (Certificate authority)	fatal	TLS only
49	Access denied	fatal	TLS only – e.g. no client certificate has been presented (TLS: Blank certificate message or SSLv3: No Certificate alert), but server is configured to require one.
50	Decode error	fatal	TLS only
51	Decrypt error	warning/fatal	TLS only
60	Export restriction	fatal	TLS only, reserved
70	Protocol version	fatal	TLS only
71	Insufficient security	fatal	TLS only
80	Internal error	fatal	TLS only
86	Inappropriate fallback	fatal	TLS only
90	User canceled	fatal	TLS only
100	No renegotiation	warning	TLS only
110	Unsupported extension	warning	TLS only
111	Certificate unobtainable	warning	TLS only
112	Unrecognized name	warning/fatal	TLS only; client’s Server Name Indicator specified a hostname not supported by the server
113	Bad certificate status response	fatal	TLS only
114	Bad certificate hash value	fatal	TLS only
115	Unknown PSK identity (used in TLS-PSK and TLS-SRP)	fatal	TLS only
116	Certificate required	fatal	TLS version 1.3 only
120 or 255	No application protocol	fatal	TLS version 1.3 only

ChangeCipherSpec protocol

TLS record format for ChangeCipherSpec protocol

Offset	Byte +0	Byte +1	Byte +2	Byte +3
Byte 0	20	N/A
Bytes 1..4	Legacy version	Length
(Major)	(Minor)	0	1
Byte 5	CCS protocol type	N/A

CCS protocol type Currently only 1. Application protocol

TLS record format for application protocol

Offset	Byte +0	Byte +1	Byte +2	Byte +3
Byte 0	23	N/A
Bytes 1..4	Legacy version	Length
(Major)	(Minor)	(bits 15..8)	(bits 7..0)
Bytes 5..(m−1)	Application data
Bytes m..(p−1)	MAC (optional)
Bytes p..(q−1)	Padding (block ciphers only)

Length Length of application data (excluding the protocol header and including the MAC and padding trailers) MAC 32 bytes for the SHA-256-based HMAC, 20 bytes for the SHA-1-based HMAC, 16 bytes for the MD5-based HMAC. Padding Variable length; last byte contains the padding length.

Support for name-based virtual servers

From the application protocol point of view, TLS belongs to a lower layer, although the TCP/IP model is too coarse to show it. This means that the TLS handshake is usually (except in the STARTTLS case) performed before the application protocol can start. In the name-based virtual server feature being provided by the application layer, all co-hosted virtual servers share the same certificate because the server has to select and send a certificate immediately after the ClientHello message. This is a big problem in hosting environments because it means either sharing the same certificate among all customers or using a different IP address for each of them.

There are two known workarounds provided by X.509:

• If all virtual servers belong to the same domain, a wildcard certificate can be used.^[286] Besides the loose host name selection that might be a problem or not, there is no common agreement about how to match wildcard certificates. Different rules are applied depending on the application protocol or software used.^[287]
• Add every virtual host name in the subjectAltName extension. The major problem being that the certificate needs to be reissued whenever a new virtual server is added.

To provide the server name, RFC 4366 Transport Layer Security (TLS) Extensions allow clients to include a Server Name Indication extension (SNI) in the extended ClientHello message. This extension hints to the server immediately which name the client wishes to connect to, so the server can select the appropriate certificate to send to the clients.

RFC 2817 also documents a method to implement name-based virtual hosting by upgrading HTTP to TLS via an HTTP/1.1 Upgrade header. Normally this is to securely implement HTTP over TLS within the main “http” URI scheme (which avoids forking the URI space and reduces the number of used ports), however, few implementations currently support this.^{[citation needed]}

Standards

Primary standards

The current approved version of TLS is version 1.3, which is specified in:

• RFC 8446: “The Transport Layer Security (TLS) Protocol Version 1.3”.

The current standard replaces these former versions, which are now considered obsolete:

• RFC 2246: “The TLS Protocol Version 1.0”.
• RFC 4346: “The Transport Layer Security (TLS) Protocol Version 1.1”.
• RFC 5246: “The Transport Layer Security (TLS) Protocol Version 1.2”.

As well as the never standardized SSL 2.0 and 3.0, which are considered obsolete:

• Internet Draft (1995), SSL Version 2.0
• RFC 6101: “The Secure Sockets Layer (SSL) Protocol Version 3.0”.

Extensions

Other RFCs subsequently extended TLS.

Extensions to TLS 1.0 include:

• RFC 2595: “Using TLS with IMAP, POP3 and ACAP”. Specifies an extension to the IMAP, POP3 and ACAP services that allow the server and client to use transport-layer security to provide private, authenticated communication over the Internet.
• RFC 2712: “Addition of Kerberos Cipher Suites to Transport Layer Security (TLS)”. The 40-bit cipher suites defined in this memo appear only for the purpose of documenting the fact that those cipher suite codes have already been assigned.
• RFC 2817: “Upgrading to TLS Within HTTP/1.1”, explains how to use the Upgrade mechanism in HTTP/1.1 to initiate Transport Layer Security (TLS) over an existing TCP connection. This allows unsecured and secured HTTP traffic to share the same well known port (in this case, http: at 80 rather than https: at 443).
• RFC 2818: “HTTP Over TLS”, distinguishes secured traffic from insecure traffic by the use of a different ‘server port’.
• RFC 3207: “SMTP Service Extension for Secure SMTP over Transport Layer Security”. Specifies an extension to the SMTP service that allows an SMTP server and client to use transport-layer security to provide private, authenticated communication over the Internet.
• RFC 3268: “AES Ciphersuites for TLS”. Adds Advanced Encryption Standard (AES) cipher suites to the previously existing symmetric ciphers.
• RFC 3546: “Transport Layer Security (TLS) Extensions”, adds a mechanism for negotiating protocol extensions during session initialisation and defines some extensions. Made obsolete by RFC 4366.
• RFC 3749: “Transport Layer Security Protocol Compression Methods”, specifies the framework for compression methods and the DEFLATE compression method.
• RFC 3943: “Transport Layer Security (TLS) Protocol Compression Using Lempel-Ziv-Stac (LZS)”.
• RFC 4132: “Addition of Camellia Cipher Suites to Transport Layer Security (TLS)”.
• RFC 4162: “Addition of SEED Cipher Suites to Transport Layer Security (TLS)”.
• RFC 4217: “Securing FTP with TLS”.
• RFC 4279: “Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)”, adds three sets of new cipher suites for the TLS protocol to support authentication based on pre-shared keys.

Extensions to TLS 1.1 include:

• RFC 4347: “Datagram Transport Layer Security” specifies a TLS variant that works over datagram protocols (such as UDP).
• RFC 4366: “Transport Layer Security (TLS) Extensions” describes both a set of specific extensions and a generic extension mechanism.
• RFC 4492: “Elliptic Curve Cryptography (ECC) Cipher Suites for Transport Layer Security (TLS)”.
• RFC 4680: “TLS Handshake Message for Supplemental Data”.
• RFC 4681: “TLS User Mapping Extension”.
• RFC 4785: “Pre-Shared Key (PSK) Ciphersuites with NULL Encryption for Transport Layer Security (TLS)”.
• RFC 5054: “Using the Secure Remote Password (SRP) Protocol for TLS Authentication”. Defines the TLS-SRP ciphersuites.
• RFC 5077: “Transport Layer Security (TLS) Session Resumption without Server-Side State”.
• RFC 5081: “Using OpenPGP Keys for Transport Layer Security (TLS) Authentication”, obsoleted by RFC 6091.

Extensions to TLS 1.2 include:

• RFC 5288: “AES Galois Counter Mode (GCM) Cipher Suites for TLS”.
• RFC 5289: “TLS Elliptic Curve Cipher Suites with SHA-256/384 and AES Galois Counter Mode (GCM)”.
• RFC 5746: “Transport Layer Security (TLS) Renegotiation Indication Extension”.
• RFC 5878: “Transport Layer Security (TLS) Authorization Extensions”.
• RFC 5932: “Camellia Cipher Suites for TLS”
• RFC 6066: “Transport Layer Security (TLS) Extensions: Extension Definitions”, includes Server Name Indication and OCSP stapling.
• RFC 6091: “Using OpenPGP Keys for Transport Layer Security (TLS) Authentication”.
• RFC 6176: “Prohibiting Secure Sockets Layer (SSL) Version 2.0”.
• RFC 6209: “Addition of the ARIA Cipher Suites to Transport Layer Security (TLS)”.
• RFC 6347: “Datagram Transport Layer Security Version 1.2”.
• RFC 6367: “Addition of the Camellia Cipher Suites to Transport Layer Security (TLS)”.
• RFC 6460: “Suite B Profile for Transport Layer Security (TLS)”.
• RFC 6655: “AES-CCM Cipher Suites for Transport Layer Security (TLS)”.
• RFC 7027: “Elliptic Curve Cryptography (ECC) Brainpool Curves for Transport Layer Security (TLS)”.
• RFC 7251: “AES-CCM Elliptic Curve Cryptography (ECC) Cipher Suites for TLS”.
• RFC 7301: “Transport Layer Security (TLS) Application-Layer Protocol Negotiation Extension”.
• RFC 7366: “Encrypt-then-MAC for Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)”.
• RFC 7465: “Prohibiting RC4 Cipher Suites”.
• RFC 7507: “TLS Fallback Signaling Cipher Suite Value (SCSV) for Preventing Protocol Downgrade Attacks”.
• RFC 7568: “Deprecating Secure Sockets Layer Version 3.0”.
• RFC 7627: “Transport Layer Security (TLS) Session Hash and Extended Master Secret Extension”.
• RFC 7685: “A Transport Layer Security (TLS) ClientHello Padding Extension”.

Encapsulations of TLS include:

• RFC 5216: “The EAP-TLS Authentication Protocol”

Informational RFCs

• RFC 7457: “Summarizing Known Attacks on Transport Layer Security (TLS) and Datagram TLS (DTLS)”
• RFC 7525: “Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)”

See also

• Application-Layer Protocol Negotiation – a TLS extension used for SPDY and TLS False Start
• Bullrun (decryption program) – a secret anti-encryption program run by the U.S. National Security Agency
• Certificate authority
• Certificate Transparency
• HTTP Strict Transport Security – HSTS
• Key ring file
• Private Communications Technology (PCT) – a historic Microsoft competitor to SSL 2.0
• QUIC (Quick UDP Internet Connections) – “…was designed to provide security protection equivalent to TLS/SSL”; QUIC’s main goal is to improve perceived performance of connection-oriented web applications that are currently using TCP
• Server-Gated Cryptography
• tcpcrypt
• DTLS
• TLS acceleration

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Further reading

Wikimedia Commons has media related to SSL and TLS.

• Wagner, David; Schneier, Bruce (November 1996). “Analysis of the SSL 3.0 Protocol” (PDF). The Second USENIX Workshop on Electronic Commerce Proceedings. USENIX Press. pp. 29–40.
• Eric Rescorla (2001). SSL and TLS: Designing and Building Secure Systems. United States: Addison-Wesley Pub Co. ISBN 978-0-201-61598-2.
• Stephen A. Thomas (2000). SSL and TLS essentials securing the Web. New York: Wiley. ISBN 978-0-471-38354-3.
• Bard, Gregory (2006). “A Challenging But Feasible Blockwise-Adaptive Chosen-Plaintext Attack on SSL”. International Association for Cryptologic Research (136). Retrieved 2011-09-23.
• Canvel, Brice. “Password Interception in a SSL/TLS Channel”. Retrieved 2007-04-20.
• IETF Multiple Authors. “RFC of change for TLS Renegotiation”. Retrieved 2009-12-11.
• Creating VPNs with IPsec and SSL/TLS Linux Journal article by Rami Rosen
• Joshua Davies (2010). Implementing SSL/TLS. Wiley. ISBN 978-0470920411.
• Polk, Tim; McKay, Kerry; Chokhani, Santosh (April 2014). “Guidelines for the Selection, Configuration, and Use of Transport Layer Security (TLS) Implementations” (PDF). National Institute of Standards and Technology. Archived from the original (PDF) on 2014-05-08. Retrieved 2014-05-07.
• Abdou, AbdelRahman; van Oorschot, Paul (August 2017). “Server Location Verification (SLV) and Server Location Pinning: Augmenting TLS Authentication”. Transactions on Privacy and Security. ACM. 21 (1): 1:1–1:26. doi:10.1145/3139294. S2CID 5869541.
• Ivan Ristic (2022). Bulletproof TLS and PKI, Second Edition. Feisty Duck. ISBN 978-1907117091.

External links

• IETF (Internet Engineering Task Force) TLS Workgroup