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In this paper, first we discuss the security model for deterministic challenge-response identification protocols. For such protocols, we are able to simplify the CR2 security model in [Bellare, Fischlin, Goldwasser, and Micali, Identification protocols secure against reset attacks: 495–511, Springer, 2001] which captures concurrent attacks and reset attacks. Then we propose an extremely simple identification protocol and prove that its CR2 security is equivalent to the hardness of the Strong Diffie–Hellman problem.

A sensor network key distribution scheme for hierarchical sensor networks was recently proposed by Cheng and Agrawal. A feature of their scheme is that pairwise keys exist between any pair of high-level nodes (which are called cluster heads) and between any (low-level) sensor node and the nearest cluster head. We present two attacks on their scheme. The first attack can be applied for certain parameter sets. If it is applicable, then this attack can result in the compromise of most if not all of the sensor node keys after a small number of cluster heads are compromised. The second attack can always be applied, though it is weaker.

In this paper, we propose a new zero-knowledge identification protocol. While the protocol consists of only two message flows, it does not rely on any underlying signature or encryption scheme. Its zero-knowledge property is preserved under concurrent composition and reset settings. It is secure under the strongest attack model which incorporates concurrent attacks, active-intruder attacks and reset attacks. Meanwhile its performance in computation and communication is close to that of the most efficient identification protocols not based on signature or encryption systems, most of which are insecure in this strong attack model.

In this paper, we investigate query processes and reconstruction functions for unconditionally secure 2-server 1-round binary private information retrieval (PIR) schemes. We begin by formulating a simplified model for PIR schemes which is equivalent to the usual model. We show that a query is equivalent to a boolean function of two variables, and we give a precise characterization of the boolean functions that can be used as "query pairs" to the two servers. We also consider several notions of "privacy" and we make a few remarks about the communication complexity of PIR schemes.