Research On Anonymous Schemes In P2P Reputation Systems Based On Trusted Computing Technology

In Peer-to-Peer (P2P) reputation systems, each peer can play two different roles: as a rater to give other peers rating values after transactions between them are completed, and as a ratee to be rated by raters. It is supposed that each peer has only one long lived pseudonym. Peers depend on the rating values given to a peer's pseudonym to evaluate the peer's trustworthiness. One serious problem in reputation systems is that all the transactions conducted by the same peer can be linked by attackers. Therefore, peers'identity privacy is a vital requirement in P2P reputation systems. Peers can hide or change their pseudonyms to protect their identity privacy. Anonymity can be used to implement such requirement. However, hiding or changing pseudonym makes the rating values bound to the ideneity be meanless, which is the conflict between the reputation system and anonymity. Whereas, in this thesis, we make further research on the above areas based on the Trusted Computing (TC) technology, mainly based on the direct anonymous attestation (DAA) protocol supported by TC, propose some efficient solutions and obtain several research achievements. The main research contents in this thesis include four aspects, which are described as follows:Firstly, we do research on TC technology, mainly focus on the DAA protocol supported by TC technology. According to the difficulties of detecting Clone Trusted Platform Module (TPM) in DAA protocol using variable basename, we propose two new methods to detect Clone TPMs, which offers TPMs high degree of anonymity. Moreover, in order to reduce the time cost of verifying the DAA signature, a new multi-signature scheme is proposed.Secondly, we propose a group-based anonymous scheme based on TC using Chord overlay, which implements peers'anonymity between peers from different groups and cen be deployed into social networks-based P2P reputation systems. Simulation is conducted in terms of anonymity degree, service selection failure rate, and time cost. The simulation results show that our scheme is robust to malicious peers and peers have high anonymity degree. In order to even the message overhed, we propose DM-Chord based on Chord protocol, which can keep an average routing hops length similar to Chord while makes the load caused by forwarding messages to distribute more evenly and increases the routing success rate.Thirdly, we porpose three anonymous schemes, self-storage high efficient anonymous scheme, blind signature-based anonymous scheme, and requester set-based anonymous scheme, which can be deployed in P2P systems that have Trusted Third Parry (TTP). The blind signature-based scheme includes two sub-schemes: scheme I and scheme II. The requester set-based anonymous scheme includes two sub-schemes: TTP server directing-based scheme and Mix-based scheme. Simulation results show that compared with existing schems, these schemes reduce the TTP server's/peers'cost, improve peers'anonymity degree, and improve the service selection success rate. Finally, we propose two anonymous schemes, DARep and EARep, which can be deployed in fully distributed P2P reputation systems. The performances of the two shcems are analyzied and compared through the simulation. The experimental results show that they have high anonymity degree and high service selection success rate.The innovation works in this thesis mainly have:1. Propose six anonymous shemes in P2P reputation systems based on TC technology. Different schems can be deployed into different applications of P2P reputation systems. The group-based anonymous scheme implements the anonymity between peers in different groups, which can be deployed in social network-based P2P reputation systems. The self-storage high efficient anonymous scheme implements all the peers'anonymity, which can be deployed into large scale P2P reputation systems that have TTP. The blind signature-based anonymous scheme and requester set-based anonymous scheme can be deployed into those P2P reputation systems that have TTP. The last two schemes, DARep and EARep, can be deployed into fully distributed P2P reputation systems.2. Propose two Clone TPM detecting methods: DAA certificate issuer-based detecting method and Chord-based detecting method, which offer TPMs high anonymity degree. The DAA certificate issuer-based detecting method depends on an online TTP, which can be deployed in those systems that have online TTP. The Chord-based detecting method can be deployed in distributed hash table (DHT) based fully distributed systems without increasing additional overhead. Analysis and simulation are conducted for our detecting methods and existing proposals. The results show that our detecting methods have high detection rate and low leak alarm rate.3. Propose an efficient and secure multi-signature scheme with the extension of DAA protocol, which mainly aims to reduce the time cost of verifying DAA signature. Analysis and simulation results show that the signer's privacy is well protected with dynamic anonymity, the public key and signatures have length independent of the number of signature members, new signers are allowed to join the signature without modifying the public key, and attacks caused by secret key dumping or leaking can be avoided.4. Propose the DM-Chord protocol. The property of routing distance among each hop was mined in Chord routing protocol. An improved routing algorithm, DM-Chord, was proposed based on Chord without modifying each peer's Finger Table. The simulation results show that, compared with Chord protocol, DM-Chord can keep an average routing hops length similar to Chord while makes the load caused by forwarding messages to distribute more evenly and increases the routing success rate when the routing source node and routing destination node are fixed and Chord is stable.