论文部分内容阅读
简介Geffe体制,指出该体制的输出序列的4种性质,并以4项定理表述了Geffe体制的特性。Geffe密码的复杂性约为10~(13),若用线性化来破译,需要知道622比特密文,且要解出622级的线性方程式。故应另找途径。文中提出两种试探破译法,其一可使密钥复杂性降为10~6,需作10~6次试探;另一可使密钥复杂性降为5.9×10~5,需作5.9×10~5次试探。二者的数级均远小于Geffe体制的密钥复杂性。文中还提出中破译超级Geffe体制的方法。
Geffe system is introduced, the four properties of output sequence of the system are pointed out, and the characteristics of Geffe system are described by four theorems. The complexity of Geffe password is about 10 ~ (13). If we use linearization to decipher, we need to know 622-bit ciphertext and solve the 622-level linear equation. So should find another way. In this paper, two methods of heuristic decipher are proposed, one of which reduces the key complexity to 10 ~ 6 and requires 10 ~ 6 explorations; the other can reduce the key complexity to 5.9 × 10 ~ 5, 10 to 5 times to test. Both are much smaller than the key complexity of the Geffe system. The article also proposed the method of deciphering Super Geffe system.