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key agreement

Two machines invent a shared secret while everyone listens, without listeners learning it.

Key agreement (ECDH) lets two parties derive a shared secret over an open channel; on its own it doesn't authenticate who the other party is.

Examples

  • In TLS, the sensor and the broker each send a key share and both compute the same secret with ECDHE, though anyone can read the shares.

  • X25519 is a common key-agreement choice; a listener who records both public halves still can't compute the secret.

See also

authenticated encryption digital signature key share
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