中文摘要：

为了对SNOW 3G加密算法进行安全性分析,提出一种改进的BDD攻击。依据线性反馈移位寄存器的反馈多项式选择特定内部比特流构造第一类OBDD。利用猜测决定攻击的思想,猜测若干有限状态机的内部状态,并寻找其与SNOW 3G加密算法输出的密钥流之间的联系来推测密码器内部比特流,以此构造第二类OBDD。将2类OBDD进行交集操作得到SNOW 3G加密算法的初始密钥。分析结果表明,改进的BDD攻击优于原BDD攻击,对SNOW 3G加密算法的安全性更具威胁。

英文摘要：

In order to analyze the security of SNOW 3Gencryption algorithm,an improved BDD attack method is proposed.The feedback polynomial of the linear feedback shift register is used to choose specific internal bit stream,which can construct the first kind of OBDD.Using the idea of guess and determine attack to guess internal state of finite state machine and find the connection between internal state and the keystream of SNOW 3Gencryption algorithm for surmising the internal bit stream of cipher,which can construct the second kind of OBDD.The initial key of SNOW 3Gencryption algorithm is obtained by the intersection operation of two kinds of OBDD.The analysis results show that the improved algorithm is better than original BDD attack and more threatening to SNOW 3Gencryption algorithm.