TLS Cipher Suites Overview

TLS Cipher Suites Overview

What is a TLS cipher suite

• TLS cipher suites: a complete set of methods (algorithm) needed to secure a network connection through TLS.
  • TLS cipher suites: a group of cipher suites (offers by SSL client in the Client Hello)
• TLS 1.2 Cipher Suite combination:
  • Key Exchange Algorithm (RSA, DH, ECDH, DHE, ECDHE, PSK)
    • > Dictates the manner by which symmetric keys will be exchanged
  • Authentication/Digital Signature Algorithm (RSA, ECDSA, DSA)
    • > Dictates how server authentication and (if needed) client authentication will be carried out.
  • Bulk Encryption Algorithm (AES, CHACHA20, Camellia, ARIA)
    • > Dictates which symmetric key algorithm will be used to encrypt the actual data.
  • Message Authentication Code Algorithm (SHA-256, POLY1305)
    • > Dictates the method the connection will use to carry out data integrity checks.

Example of TLS 1.2 cipher suite

TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256

• TLS is the protocol
• ECDHE is the key exchange algorithm
• ECDSA is the authentication/signature algorithm
• AES_128_GCM is the bulk encryption algorithm
  • AES with 128-bit key using GCM (Galois/Counter Mode) as mode of operation
• SHA256 is the MAC / hash algorithm
  • SHA with 256-bit key

The most secure algorithms are:

• TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
• TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
• TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
• TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
• TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305
• TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305

They have Perfect Forward Secrecy and Authenticated Encryption.

The mid-secure (warning) algorithms are:

• TLS_ECDHE_ECDSA_WITH_RC4_128_SHA
• TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
• TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
• TLS_ECDHE_RSA_WITH_RC4_128_SHA
• TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
• TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
• TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
• TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
• TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256

They have Perfect Forward Secrecy but no Authenticated Encryption.

The dangerous algorithms are:

• TLS_RSA_WITH_RC4_128_SHA
• TLS_RSA_WITH_3DES_EDE_CBC_SHA
• TLS_RSA_WITH_AES_128_CBC_SHA
• TLS_RSA_WITH_AES_256_CBC_SHA
• TLS_RSA_WITH_AES_128_CBC_SHA256
• TLS_RSA_WITH_AES_128_GCM_SHA256
• TLS_RSA_WITH_AES_256_GCM_SHA384

They have no Perfect Forward Secrecy.

Example of TLS 1.3 cipher suite

TLS_AES_256_GCM_SHA384

• TLS is the protocol
• AES_256_GCM is the bulk encryption algorithm
  • AES with 256-bit key using GCM (Galois/Counter Mode) as mode of operation
• SHA384 is the MAC / hash algorithm
  • SHA with 384-bit key
• Signature algorithms are now negotiated independently, no longer listed in the cipher suite
  • There are two extensions for indicating which signature algorithms may be used in digital signatures
    • > “signature_algorithms_cert” extension
    • > “signature_algorithms” extension
  • It supports RSA and ECDSA
• Key exchange algorithms are now negotiated independently, using the “supported_group” extension
  • It support ECDHE and DHE

TLS 1.3 has eliminated:

• SSL Compression
• Static key exchange functions
• Block ciphers (CBC)
• Non-AEAD ciphers (MAC-then-Encrypt)
• Renegotiation of encryption parameters

It’s also dropped support for older, vulnerable SSL ciphers like:

• RC4, DSA, MD5, SHA1
• Weak Elliptic Curves, RSA Key Exchange, Static Diffie-Hellman (DH, ECDH)

Recommended cipher suites list 

• TLS_AES_256_GCM_SHA384
• TLS_CHACHA20_POLY1305_SHA256
• TLS_AES_128_GCM_SHA256
• TLS_AES_128_CCM_8_SHA256
• TLS_AES_128_CCM_SHA256