Extending NCP for protocols using public keys One of the greatest obstacles to widespread deployment of wireless mobile systems is security. Cryptographically strong protocols and algorithms are required to enable secure communication over links that are easy to monitor and control by an attacker. While good cryptographic algorithms exist, it is difficult to design protocols that are immune to malicious attack. Good analysis techniques are lacking. This paper presents extensions to a technique for specifying and analyzing nonmonotonic cryptographic protocols that use asymmetric keys. We introduce new actions and inference rules, as well as slight modifications to the Update function. An important observation is that reasoning about the origin of messages is quite different when dealing with asymmetric key protocols. We also introduce the notion that keys in certificates should be bound to the principals receiving them. We extend the technique to meet the binding requirements and show how the flaw in the Denning and Sacco public key protocol, which was discovered by Abadi and Needham, is revealed. We demonstrate the extended technique using one protocol of our own and the Needham and Schroeder public key protocol. We also introduce and analyze a fix to a known weakness in Needham and Schroederu0027s protocol using our extended technique. Finally, we present several applications of these techniques to protocols for mobile computing over wireless networks.

Efficient provablysecure privacypreserving signaturebased key establishment protocol Abstract   Assuring the security and privacy of users in todayxe2x80x99s evergrowing digital communications is of prime significance. In a digital communication, in order to preserve the identities and confidential information of individuals, and more significantly, to prevent any unauthorized access and manipulation, the user and server need to establish a shared key. In recent years, a number of key establishment protocols have been put forward to keep the integrity, confidentiality, and anonymity of participants. Nonetheless, investigating the literature reveals the fact that the existing schemes cannot entirely assuage the desired security requirements. Therefore, in this paper, considering the computational efficiency, we propose a novel privacypreserving signaturebased key establishment protocol, which can guarantee subsequent secure communications of users and servers. To indicate that the proposed scheme can withstand the known attacks, we present a rigorous formal security proof and verification by utilization of two stateoftheart techniques, i.e., the random oracle model and ProVerif tool. Further, to show that the proposed protocol has proper performance, we compare our scheme with several recentlypublished schemes. The achieved results evince that the proposed scheme has a proper level of efficiency and is the best in terms of security provision.