TLS_AES_256_GCM_SHA384
TLS_AES_256_GCM_SHA384
TLS_AES_256_GCM_SHA384 is a TLS 1.3 cipher suite using AES-256 in GCM mode. It provides 256-bit symmetric encryption, which is required by some compliance frameworks (FIPS 140-2, some government standards). Marginally slower than AES-128-GCM on hardware without AES-NI; effectively equivalent in security for all practical threat models.
Key Exchange
ECDHE (built into TLS 1.3 handshake)
Authentication
Signature algorithm negotiated separately
Encryption
AES-256-GCM
MAC / Integrity
SHA-384 (AEAD – integrated)
Details
AES-256-GCM offers 256-bit security, which exceeds the requirements for any currently known attack. The extra key length is primarily relevant for post-quantum scenarios and regulatory compliance. On modern hardware with AES-NI instruction support, AES-256-GCM is only ~15% slower than AES-128-GCM. Preferred for high-security environments and FIPS compliance.