Practical Attacks on a Cryptosystem Proposed in Patent WO/2009/066313

摘要

A new cryptosystem is proposed in the international patent WO/2009/066313 by Artus. The symmetric-key primitive in the cryp tosystem resembles a stream cipher. The system differs markedly from cryptosystems used today in that the secret key is changed with the plaintext. The patent does not discuss key management (generation, transmission) in sufficient detail. Some of the proposed methods for transmission of keys are highly insecure and an algorithm for key gen eration is missing. In this paper, we find that related-key attacks of negligibly low complexity (data/time) can result when certain (flawed) key generation algorithms are used. We also present a negligibly-low-complexity attack in a non-related-key setting. We hope that the results caution potential users of the cryptosystem.