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transcript hash
A running fingerprint of every handshake message, used to lock the keys to what was actually said.
During a TLS handshake, both sides keep a hash of all messages exchanged so far. The derived keys are bound to this transcript hash, so if an attacker tampered with any handshake message, the fingerprints won't match and the connection fails. It cryptographically guarantees both parties saw the same negotiation.
See also
- traffic secret / traffic keysThe per-direction keys TLS derives to encrypt the actual data flowing each way.
- TLS 1.3The current, streamlined version of the TLS encryption protocol.
- TLS 1.3 record layerThe part of TLS 1.3 that chops the data stream into chunks and encrypts each one.