CRYPTOGRAPHIC DATA INTEGRITY APPARATUS AND METHOD BASED ON PSEUDO-RANDOM BIT GENERATORS

摘要

A cryptographic method to ensure data integrity is disclosed.It uses pseudo-random bit generators. An apparatusimplementing the method is also disclosed. The method providesdata integrity protection and confidentiality protection atonce, using a shared secret key. A variant provides dataintegrity protection only, using a shared secret key. Avariant of the disclosed method lifts the restriction onre-use of a secret key in the case of a stream cipher. Yetanother variant provides a secure hash function of the typeused in digital signature schemes, this time requiring nosecret key. For each bit of the original message, the presentinvention uses one of ten independent pseudo-random bitgenerators as a key stream source for double stream cipherencryption. A unique heuristic algorithm changes the followinggenerator selection out of the group of ten. This arrangementcorresponds to a new definition for a "perfect data integritycipher", where the illicit modification of a single bit in theciphertext causes a permanent and random alteration of theremaining portion of the message recovered by the legitimatereceiver. The disclosed method improves the cryptographicsecurity of pseudo-random generation algorithms.