SoK: Lessons Learned from SSL/TLS Attacks

Since its introduction in 1994 the Secure Socket Layer (SSL) protocol (later renamed to Transport Layer Security (TLS)) evolved to the de facto standard for securing the transport layer. SSL/TLS can be used for ensuring data confidentiality, integrity and authenticity during transport. A main feature of the protocol is flexibility: Modes of operation and security aims can easily be configured through different cipher suites. However, during the evolutionary development several flaws were found. This paper presents an overview on theoretical and practical attacks of the last 17 years, in chronological order and four categories: Attacks on the Handshake protocol, on the Record and Application Data Protocols, on the PKI infrastructure and various other attacks. We try to give a short "Lesson(s) Learned" at the end of each paragraph.