Research On Some Issues Of Trust

The trust relationship is very important in cyberspace. In this dissertation, the trust is studied in several different applications. The major contributions of this dissertation are summarized as follows:1. To estimate the trust value in P2P networks, an autonomous trust mode based on both direct experiences and recommendations was proposed, in which the recommendation synthetic coefficients were decided by the trustor's trust on the recommendation subscribers. Both the direct trust and the recommendation trust were attenuated with the time intervals. Corresponding data structure and an iterative compute method were given.2. A decision system with trust and risk estimation in a P2P transaction environment is presented. It is used to help an entity to make a decision on whether a potential transaction should be made or not according to its own risk attitude on the basement of its observation on past transaction gains and other entities'recommendations. The gain rate as the ration of the transaction gain to the risk investment of a transaction is used to measure the risk in Mean-Deviation preferences. An iterative method to update the mean and deviation of gain rate is proposed to keep both the storage resource and the computational complexity constant. Simulation results using Matlab indicate that TRUSTEngin can help entities making more wealth in risky transaction environments.3. An attack to current interface copy protection systems is given, named as interface replacement attack. A novel content proctection framework is proposed to restrict contents flowing within legal devices. The new framework deploys security mechanisms in both interior part of a consumer electronic device and interfaces on it. The framework is adopted by the Chinese industry standard SJ/T 11407.1-2009.4. An identity-based chameleon hash function without the key escrow problem is proposed. It not only achieves all the desired security properties of the traditional identity-based chameleon hashing but also removes the inherent escrow problem of identity-based systems. That is, the private key generator (PKG) can not find a collision of our proposed identity-based chameleon hash function. Moreover, an identity-based chameleon signature without the key escrow problem is given by adoption of the identity-based encryption and the identity-based signature without the key escrow. Besides, a security proof of the proposed chameleon hashing and signature scheme is given, showing that these schemes without the key escrow are collision resistance, semantically secure, message hiding.5. An identity-based key-exposure free chameleon hashing based on the RSA assumption is proposed as the first one. Based on well established hash-and-sign paradigm, an identity-based key-exposure free chameleon signature is also proposed. These schemes also give a positive answer for the open problem introduced by Giuseppe Ateniese and de Mederious in 2005. Besides, a security proof of the proposed chameleon hashing and signature scheme is given, showing that these schemes without the key-exposure are collision resistance, semantically secure, message hiding.