Search

A strong designated verifier signature (SDVS) is a variation of traditional digital signatures, since it allows a signer to designate an intended receiver as the verifier rather than anyone. To do this, a signer must incorporate the verifier's public key with the signing procedure such that only the intended receiver could verify this signature with his/her private key. Such a signature further enables a designated verifier to simulate a computationally indistinguishable transcript intended for himself. Consequently, no one can identify the real signer's identity from a candidate signer and a designated verifier, which is referred to as the property of signer ambiguity. A strong notion of signer ambiguity states that no polynomial-time adversary can distinguish the real signer of a given SDVS that is not received by the designated verifier, even if the adversary has obtained the signer's private key. In 2013, Islam and Biswas proposed a provably secure certificateless strong designated verifier signature (CL-SDVS) scheme based on bilinear pairings. In this paper, we will demonstrate that their scheme fails to satisfy strong signer ambiguity and must assume a trusted private key generator (PKG). In other words, their CL-SDVS scheme is vulnerable to both key-compromise and malicious PKG attacks. Additionally, we present an improved variant to eliminate these weaknesses.

This paper proposes two metrics for evaluating the low probability of detection (LPD) performance in cooperative wireless communication networks. One metric is the distance ration between the minimum range of all the interceptor-relay/transmitter pairs and the intended transmitter-destination distance. Another is the ratio between the average range of all interceptor-relay/transmitter pairs and the intended transmitter-destination distance. The two metrics are compared with the distance ratio defined for the point-to-point communication systems with a simple relay network topology. The results show that the cooperative networks exhibit worse LPD performance than the point-to-point systems when the same receivers are used in both cooperative network and point-to-point system.