Hybrid Mobile Security Protocol: Formal Verification using a New Modal Logic

Hybrid cryptographic security protocols find applications in many areas of communications, none more demanding than in the mobile security sector. In recent years a number of hybrid cryptographic security protocols have been proposed for use with 3G mobile systems. These include the ASPeCT [1] and Boyd-Park [2] security protocol. These protocols use a public key algorithm to exchange a secret session key for use with a symmetric algorithm, thereby removing the need for ultra reliable key servers. In order to provide assurance that these protocols are verifiably secure and trustworthy it is necessary to perform a formal verification on their design specifications. In this paper the Boyd-Park hybrid mobile security protocol is formally verified using a new extended modal logic technique. This logic is based on the Coffey-Saidha logic [3], which was designed to verify public key based protocols only. The logic presented in this paper is a substantial extension to the original. As a result of this verification a modification to the original Boyd-Park protocol is suggested. Key-Words: Formal methods, verification logic, hybrid security protocol, 3G mobile