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.

Private Authentication: Optimal Information Theoretic Schemes The main security service in the connected world of cyber physical systems necessitates to authenticate a large number of nodes privately. In this paper, the private authentication problem is considered, that consists of a certificate authority, a verifier, many legitimate users (prover) and any arbitrary number of illegitimate users. Each legitimate user wants to be authenticated (using his personal key) by the verifier, while simultaneously wants to stay completely anonymous (even to the verifier and the CA). On the other hand, an illegitimate user must fail to authenticate himself. We analyze this problem from an information theoretical perspective. First, we propose a general interactive informationtheoretic model for the problem. As a metric to measure the reliability, we consider the authentication key rate whose rate maximization has a tradeoff with establishing privacy. Then, we analyze the problem in two different regimes: finite size regime (i.e., the variables are elements of a finite field) and asymptotic regime (i.e., the variables are considered to have large enough length). For both regimes, we propose schemes that satisfy the completeness, soundness and privacy properties. In finite size regime, the idea is to generate the authentication keys according to a secret sharing scheme. In asymptotic regime, we use a random binning based scheme which relies on the joint typicality to generate the authentication keys. Moreover, providing the converse proof, we show that our scheme achieves capacity in the asymptotic regime. For finite size regime our scheme achieves capacity for large field size.