Wide Mouth Frog

See also: Cryptography | Public-Key Cryptosystem

A system of secret exchange using a mutually trusted third party. It is also known as the Otway-Rees Protocol. The original idea used symmetric cipher keys, however, this method can be extended to use public key algorithms, nonces, digests and other techniques to improve on security.

When Alice wants to talk to Bob she asks Troy, the trusted third party, to assist in the key exchange.

The process is as follows:

A – Identity or location of Alice

B – Identity or location of Bob

Ka – Key shared between Troy and Alice

Kb – Key shared between Troy and Bob

Sab – Secret shared between Alice and Bob for session communication


Alice -> Troy {B,Sab}Ka

Troy -> Bob {A,Sab}Kb

In this manner Alice uses Troy to securely share a secret with Bob.

TakeDown.NET -> “Wide-Mouth-Frog