Interlock protocol

The interlock protocol, as described by Ron Rivest and Adi Shamir, was designed to frustrate eavesdropper attack against two parties that use an anonymous key exchange protocol to secure their conversation. A further paper proposed using it as an authentication protocol, which was subsequently broken. The interlock protocol, as described by Ron Rivest and Adi Shamir, was designed to frustrate eavesdropper attack against two parties that use an anonymous key exchange protocol to secure their conversation. A further paper proposed using it as an authentication protocol, which was subsequently broken. Most cryptographic protocols rely on the prior establishment of secret or public keys or passwords. However, the Diffie–Hellman key exchange protocol introduced the concept of two parties establishing a secure channel (that is, with at least some desirable security properties) without any such prior agreement. Unauthenticated Diffie–Hellman, as an anonymous key agreement protocol, has long been known to be subject to man in the middle attack. However, the dream of a 'zipless' mutually authenticated secure channel remained. The Interlock Protocol was described as a method to expose a middle-man who might try to compromise two parties that use anonymous key agreement to secure their conversation.