Formal Analysis of Multi-Party Contract Signing

We analyze the multi-party contract-signing protocols of Garay and MacKenzie (GM) and of Baum and Waidner (BW). We use a finite-state tool, MOCHA, which allows specification of protocol properties in a branchingtime temporal logic with game semantics. While our analysis does not reveal any errors in the BW protocol, in the GM protocol we discover serious problems with fairness for four signers and an oversight regarding abuse-freeness for three signers. We propose a complete revision of the GM subprotocols in order to restore fairness.

• Type: Conference
• Year: 2004
• Where: CSFW
• Authors: Rohit Chadha, Steve Kremer, Andre Scedrov
• Keywords: Branchingtime Temporal Logic, CSFW 2004, GM Protocol, Multi-party Contract-signing Protocols, Security Privacy