Abstract. Certificateless public key cryptography (CLPKC) is a paradigm to solve the inherent key escrow problem suffered by identity-based cryptography (IBC). While certificateless signature is one of the most important security primitives in CLPKC, there are relatively few proposed schemes in the literature. In this paper, we manage to construct an efficient certificateless signature scheme based on the intractability of the computational Diffie-Hellman problem. By using a shorter public key, two pairing computations can be saved in the verification algorithm. Besides, no pairing computation is needed in the signing algorithm. The proposed scheme is existential unforgeable in the random oracle model. We also present an extended construction whose trust level is the same as that of a traditional signature scheme.

By combining techniques of watermarking and fingerprinting, a sound buyer-seller watermarking protocol can address the issue of copyright protection in e-commerce. In this paper, we analyze the security of two recent anonymous buyer-seller watermarking protocols proposed by Ju et. al and Choi et. al respectively, and prove that they do not provide the features and security as claimed. In particular, we show that i) the commutative cryptosystem used in Choi et. al 's protocol fails to prevent the watermark certification authority (WCA) from discovering the watermark (fingerprint) chosen by the buyer; ii) for both protocols, the seller can discover the watermark chosen by the buyer if he colludes with the WCA. Hence, these protocols cannot guard against conspiracy attacks. We further show that these protocols only provide "partial" anonymity, ie. the buyer's anonymity is guaranteed only if WCA is honest. Our results suggest that the security of these protocols must assume the honesty of WCA, contrary to the designers' original claim. Finally, we propose a new anonymous buyer-seller watermarking protocol which is more secure and efficient, and provides true anonymity.

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Gender is an important demographic attribute of people. This paper provides a survey of human gender recognition in computer vision. A review of approaches exploiting information from face and whole body (either from a still image or gait sequence) is presented. We highlight the challenges faced and survey the representative methods of these approaches. Based on the results, good performance have been achieved for datasets captured under controlled environments, but there is still much work that can be done to improve the robustness of gender recognition under real-life environments.

In this paper, we propose a new variant of the NTRU public key cryptosystem − the MaTRU cryptosystem. MaTRU works under the same general principles as the NTRU cryptosystem, except that it operates in a different ring with a different linear transformation for encryption and decryption. In particular, it operates in the ring of k by k matrices of polynomials in R = Z[X]/(X n − 1), whereas NTRU operates in the ring Z[X]/(X N − 1). Note that an instance of MaTRU has the same number of bits per message as an instance of NTRU when nk 2 = N . The improved efficiency of the linear transformation in MaTRU leads to respectable speed improvements by a factor of O(k) over NTRU at the cost of a somewhat larger public key.