Digital signature is one of the most important cryptographic primitives. We proposed a new digital signature scheme based on Catalano’s trapdoor. Since Catalano’s trapdoor is more efficient than existing trapdoors in number theory, our scheme need not modular exponentiation but several modular multiplications in the signing algorithm. We also proved our scheme is provably secure against adap-tively chosen message attack by using the Forking lemma.
Software systems in distributed environment are changing from a close and relatively static form, whose users are familiar with each other, to an open and highly dynamic mode, which can be visited by public. In such circumstance, trust evalua-tion model becomes focus of intense research at current time. Trust evaluation model establishes a management framework of trust relationship between entities, involving expression and measurement of trust, comprehensive calculation of direct trust value and recommended trust value, and recognition of malicious entities and recommendations. Based on the analysis of several typical trust evaluation models, the classification of trust evalua-tion ideas and modes is discussed, the questions existing in current research and the directions of future research are pointed out.
