A New Approach to Server-Aided Secret Computation

. Server-Aided Secret Computation(SASC) protocol enables the client(smart card) to borrow the computing power from the server(un trusted auxiliary device like ATM) without revealing the secret information of the client. The previous approach is to decompose the client's secret information into many pieces and to reveal some of them to the server. It significantly accelerates the secret computation, however there are some problems. Firstly, many pieces that have linear relation enable an attacker to probabilistic active attack, and it causes the performance degradation of SASC protocol. Secondly, the amount of communication and the server's computation is very large and proportional to security parameters. In this paper, we investigate a new approach to SASC protocol for RSA signature generation. Our approach is to blind the client's secret information by using a series of random numbers rather than to decompose it. The proposed protocol is secure against all known attacks including the..