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分析了一个新型流密码体制——COSvd(2,128)的安全性.COSvd(2,128)使用了钟控非线性反馈移位寄存器(NLFSR)和由混沌序列控制的S-盒,设计者声称COSvd(2,128)能够抵抗已知的任何攻击.然而,分析表明,该流密码体制的S-盒设计存在严重漏洞,它所产生密钥流的字节分布严重不均衡,在一些很重要的广播加密场合,这一漏洞会导致成功概率很高的唯密文攻击;此外,该流密码体制的其他构件的设计也存在许多漏洞,根据这些漏洞提出了一个分别征服攻击,该攻击能够从O(226)字节的已知明文恢复出COSvd(2,128)的所有密钥,其成功概率可达93.4597%,复杂度为O(2113),显然这种攻击的复杂度大大低于穷搜索的复杂度2512.
The security of a new stream cipher system, CISCO (2,128), is analyzed.Cosvd (2,128) uses a clocked nonlinear feedback shift register (NLFSR) and an S-box controlled by a chaotic sequence, ) Can resist any known attacks.However, the analysis shows that there is a serious loophole in the S-box design of the stream cipher system, and the byte distribution of the keystream generated by it is seriously unbalanced. In some important broadcast encryption occasions, This vulnerability leads to a ciphertext-only attack with a high probability of success. In addition, there are many vulnerabilities in the design of other components of the stream cipher system. According to these vulnerabilities, a separate conquered attack is proposed, which can attack O (226) The known plaintext of Section retrieves all the keys of COSVD (2,128) with a success probability of 93.4597% and a complexity of O (2113). Obviously the complexity of this attack is much lower than the complexity of poor search 2512.