对Wang Shihong的“Chaos-based secure communication in a large community”一文提出的混沌序列密码算法进行了分析,发现该加密算法产生的加密乱数序列的前若干值对密钥低位比特的变化不敏感。据此利用已知明文攻击,对该算法提出了...对Wang Shihong的“Chaos-based secure communication in a large community”一文提出的混沌序列密码算法进行了分析,发现该加密算法产生的加密乱数序列的前若干值对密钥低位比特的变化不敏感。据此利用已知明文攻击,对该算法提出了分割攻击方案,并分析了该攻击方案的成功率和计算复杂性。针对该加密算法存在的弱点给出了可能的改进措施,并证明了其有效性。展开更多
In this paper, we analyze the security of a new stream cipher-COSvd（2,128）. This cipher was proposed by E. Filiol et al. at the ECRYPT SASC＇2004 （The State of the Art of Stream Ciphers）. It uses clock-controlled ...In this paper, we analyze the security of a new stream cipher-COSvd（2,128）. This cipher was proposed by E. Filiol et al. at the ECRYPT SASC＇2004 （The State of the Art of Stream Ciphers）. It uses clock-controlled non-linear feedback registers together with an S-box controlled by a chaotic sequence and was claimed to prevent any existing attacks. However, our analysis shows that there are some serious security flaws in the design of the S-box, resulting in heavy biased byte distribution in the keystream. In some broadcast applications, this flaw will cause a ciphertext-only attack with high success rate. Besides, there are also many security flaws in other parts of the cipher. We point out these flaws one by one and develop a divide-and-conquer attack to recover the secret keys from O（2^26）-byte known plaintext with success rate 93.4597% and complexity O（2^113）, which is much lower than 2^512, the complexity of exhaustive search.展开更多
文摘对Wang Shihong的“Chaos-based secure communication in a large community”一文提出的混沌序列密码算法进行了分析,发现该加密算法产生的加密乱数序列的前若干值对密钥低位比特的变化不敏感。据此利用已知明文攻击,对该算法提出了分割攻击方案,并分析了该攻击方案的成功率和计算复杂性。针对该加密算法存在的弱点给出了可能的改进措施,并证明了其有效性。
基金supported by the National Natural Science Foundation of China(Grant Nos.60273027,60373047)the National Grand Fundamental Research 973 Program of China(Grant No.2004CB318004).
文摘In this paper, we analyze the security of a new stream cipher-COSvd（2,128）. This cipher was proposed by E. Filiol et al. at the ECRYPT SASC＇2004 （The State of the Art of Stream Ciphers）. It uses clock-controlled non-linear feedback registers together with an S-box controlled by a chaotic sequence and was claimed to prevent any existing attacks. However, our analysis shows that there are some serious security flaws in the design of the S-box, resulting in heavy biased byte distribution in the keystream. In some broadcast applications, this flaw will cause a ciphertext-only attack with high success rate. Besides, there are also many security flaws in other parts of the cipher. We point out these flaws one by one and develop a divide-and-conquer attack to recover the secret keys from O（2^26）-byte known plaintext with success rate 93.4597% and complexity O（2^113）, which is much lower than 2^512, the complexity of exhaustive search.
