Cipher Suite Selection and Prioritization

Cipher Suite Selection and Prioritization

Cipher suite configuration significantly impacts both security and performance. Modern deployments should prioritize Authenticated Encryption with Associated Data (AEAD) cipher suites, particularly those using AES-GCM and ChaCha20-Poly1305. These cipher suites provide both confidentiality and integrity protection in a single operation, improving performance and reducing implementation complexity.

Forward secrecy represents a critical security property that protects past communications even if server private keys are compromised. Ephemeral Diffie-Hellman (ECDHE and DHE) key exchanges provide forward secrecy by generating unique keys for each session. Organizations should exclusively use cipher suites supporting forward secrecy, removing static RSA key exchange options.

The order of cipher suites matters when server-side preference is enabled. Servers should list cipher suites in order of decreasing security and performance, allowing the best mutually supported option. ECDHE-ECDSA combinations offer optimal performance, followed by ECDHE-RSA. AES-128 provides sufficient security for most applications while offering better performance than AES-256.

Removing weak cipher suites eliminates potential vulnerabilities. Export-grade ciphers, NULL encryption, anonymous authentication, and DES-based ciphers must be disabled. RC4, once widely used, contains serious weaknesses and should be removed. MD5 and SHA-1 hash functions in cipher suites face deprecation due to collision attacks. Regular reviews ensure new vulnerable ciphers are promptly disabled.