A cipher suite is a combination of a key exchange algorithm, authentication method, bulk encryption cipher, and message authentication code.
In a cryptosystem like TLS, the client and server must agree on a cipher suite before they can begin communicating securely. A typical cipher suite looks like ECDHE_RSA_WITH_AES_128_GCM_SHA256 or ECDHE-RSA-AES128-GCM-SHA256, indicating:
- ECDHE (elliptic curve Diffie-Hellman ephemeral) for key exchange
- RSA for authentication
- AES-128 as the cipher, with Galois/Counter Mode (GCM) as the block cipher mode of operation
- SHA-256 as the hash-based message authentication code (HMAC)