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pre-shared key (PSK)
A secret both sides already agreed on beforehand, used to bootstrap secure communication without a fresh negotiation.
In secure protocols like TLS 1.3, a pre-shared key is a secret established in advance (or carried over from a previous session) that feeds directly into deriving the connection's encryption keys. It lets two parties skip parts of the handshake and start protected communication faster. It becomes an input to the 'early secret,' the first value in TLS 1.3's key-derivation chain.
See also
- record layerThe part of TLS that chops your data into chunks and encrypts each one for sending.
- RFC 8448An official document that walks through a complete example TLS 1.3 connection, byte by byte, for testing.
- PKCS#1 v1.5An older standard way to pad data before RSA signs it, whose loose parsing has historically let attackers forge signatures.