First-order Verification of Cryptographic Protocols

We describe a verification method for cryptographic protocols, based on first-order invariants. For typical protocols, a suitable invariant can be generated mechanically from the program text, allowing safety properties to be proved by ordinary first-order reasoning. The method has been implemented in an automatic verifier, TAPS, that proves safety properties comparable to those in published Isabelle verifications, but does so much faster with little or no guidance from the user. TAPS has verified properties of about 80 protocols, including all but three protocols from the Clark & Jacob survey; on average, these verifications require less than a second of CPU time and less than 4 bytes of hints from the user.