Protocol 5

Protocol assumptions

Protocol 5, depicted in the illustration below, is very similar to Protocol 1 except that the nonce generated by Bob is replaced by a timestamp generated by Bob.

These assumptions are the same as the assumptions for Protocol 1, except that the need for Bob to have a source of randomness is replaced by the following:

• Bob can generate and verify integrity-protected timestamps: This requires Bob to have a system clock. Requiring $T_B$ to be integrity-protected means an attacker can’t manipulate it without subsequent detection by Bob.