Protocols & PKIAcceptable
TLS 1.2
Secure transport protocol
How it works
TLS 1.2 (RFC 5246, 2008) negotiates a cipher suite, authenticates the server with an X.509 certificate, agrees session keys and then protects application data. It supports many options, including RSA key transport, static and ephemeral DH, CBC and GCM suites. Its safety depends on disabling the weak options.
Status: Safe when configured with ECDHE and AEAD cipher suites only.
Strengths
- Universally supported
- Supports AEAD suites (AES-GCM, ChaCha20-Poly1305) and ECDHE forward secrecy
Weaknesses and known attacks
- Weak configurations remain possible: RSA key exchange (no forward secrecy, ROBOT), CBC suites (Lucky Thirteen), 3DES (Sweet32) and RC4.
- Older handshake and renegotiation designs led to attacks that TLS 1.3 removed by design.
Use it for
- Compatibility with clients that do not yet support TLS 1.3
Don't use it for
- RSA key exchange, CBC, 3DES or RC4 cipher suites
Exam tip
A secure TLS 1.2 configuration uses ECDHE for key exchange and AES-GCM for encryption. Anything with RSA key exchange lacks forward secrecy.