Stream Cipher-Based Hash Function and Its Security.

Stream cipher-based hash function (SCH) is the one of new approachs to construct hash functions. However, the security and the design policy of SCH have not yet been studied sufficiently. In this paper, we analyze the security of SCHs focusing on the stream cipher function. First, we propose a model of SCHs which consist of a pre-computation function and a stream cipher. Then, we show that attacks against a stream cipher can also be threats to SCHs and discuss the security on each phase of SCH; message injection, blank rounds, and hash generation. Finally we derive the necessary conditions on the stream cipher function for an SCH to be secure.