文件名称：NP学习笔记3 BYPASS NP
文件大小：11KB
文件格式：TXT
更新时间：2013-06-13 12:35:37
NP学习笔记3 BYPASS NP
This has been a description of how to use the DES algorithm to encrypt one 64-bit block. To decrypt, use the same process, but just use the keys K[i] in reverse order. That is, instead of applying K[1] for the first iteration, apply K[16], and then K[15] for the second, on down to K[1]. Summaries: Key schedule: C[0]D[0] = PC1(key) for 1 <= i <= 16 C[i] = LS[i](C[i-1]) D[i] = LS[i](D[i-1]) K[i] = PC2(C[i]D[i]) Encipherment: L[0]R[0] = IP(plain block) for 1 <= i <= 16 L[i] = R[i-1] R[i] = L[i-1] xor f(R[i-1], K[i]) cipher block = FP(R[16]L[16]) Decipherment: R[16]L[16] = IP(cipher block) for 1 <= i <= 16 R[i-1] = L[i] L[i-1] = R[i] xor f(L[i], K[i]) plain block = FP(L[0]R[0])