A Study on Construction and Security of Computer-Aided Security Schemes

CPU performance has been increasing continually. To resist attacks in such a technological environment, we must increase the entropy of secrets. However, the progress of CPU performance benefits not only attackers but also legitimate users. Security schemes specifically designed to enhance legitimate users' security by exploiting CPU performance have been proposed. In this paper, we call such schemes "computer-aided security schemes" (CASS) and classify them into two types in terms of the aiding mechanism. We propose general constructions and provide a security proof of CASS for one type. We discuss the feasibility of CASS in this type, and show that an increase in the length of a password, which a legitimate user should memorize, can be suppressed by using CASS of this type even if CPU performance increases in the future.