Unauthorized tampering with outsourced data can result in significant losses for both data owner and users.Data integrity therefore becomes an important factor in outsourced data systems.In this paper,we address this problem and propose a scheme for verifying the integrity of outsourced data.We first propose a new authenticated data structure for authenticating membership queries in sets based on accumulators,and then show how to apply it to the problem of verifying the integrity of outsourced data.We also prove that our scheme is secure under the q-strong DiffieHellman assumption.More importantly,our scheme has the constant cost communication,meanwhile keeping other complexity measures constant.Compared to previous schemes based on accumulators,our scheme reduces update cost and so improves previous schemes based on accumulators.In addition,the experimental comparison shows that our scheme outperforms the previous schemes.
WANG XiaomingYU FangLIN YanchunGAN QingqingWU Daini
Coalition logic （CL） is one of the most influential logical formalisms for strategic abilities of multi-agent systems. CL can specify what a group of agents can achieve through choices of their actions, denoted by [C]φ to state that a group of agents C can have a strategy to bring about φ by collective actions, no matter what the other agents do. However, CL lacks the temporal dimension and thus can not capture the dynamic aspects of a system. Therefore, CL can not formalize the evolvement of rational mental attitudes of the agents such as knowledge, which has been shown to be very useful in specifications and verifications of distributed systems, and has received substantial amount of studies. In this paper, we introduce coalition logic of temporal knowledge （CLTK）, by incorporating a temporal logic of knowledge （Halpern and Vardi＇s logic of CKLn） into CL to equip CL with the power to formalize how agents＇ knowledge （individual or group knowledge） evolves over the time by coalitional forces and the temporal properties of strategic abilities as well. Furthermore, we provide an axiomatic system for CLTK and prove that it is sound and complete, along with the complexity of the satisfiability problem which is shown to be EXPTIME-complete.
