Question 1

How do I read a TLS cipher suite name?

Accepted Answer

A TLS 1.2 name like TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 lists the key exchange (ECDHE), the authentication (RSA), the bulk cipher and mode (AES-128-GCM), and the MAC/PRF hash (SHA256). TLS 1.3 shortens this to just the cipher and hash, e.g. TLS_AES_128_GCM_SHA256, because the handshake fixes the rest.

Question 2

What makes a cipher suite weak or deprecated?

Accepted Answer

Red flags include RC4 (biased keystream, banned by RFC 7465), 3DES (64-bit blocks, vulnerable to Sweet32), NULL (no encryption at all), static RSA key exchange (no forward secrecy), and old CBC constructions prone to padding-oracle attacks. Strong suites use AEAD ciphers (AES-GCM or ChaCha20-Poly1305) with an ephemeral key exchange for forward secrecy.

Question 3

What is forward secrecy and why does it matter?

Accepted Answer

Forward secrecy means each session uses a fresh, ephemeral key (from ECDHE or DHE), so recording encrypted traffic today and stealing the server's long-term private key later still does not decrypt past sessions. Suites using static RSA key exchange lack it, which is a major reason they are deprecated.

TLS Cipher Sort

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