Here is the Sage code copy from Cryptography and Network Security Principle and Practice 5th by Stallings in Appendix B of SDES Sage code:
P10_data = [3, 5, 2, 7, 4, 10, 1, 9, 8, 6]; P8_data = [6, 3, 7, 4, 8, 5, 10, 9]; LS1_data = [2, 3, 4, 5, 1]; LS2_data = [3, 4, 5, 1, 2]; IP_data = [2, 6, 3, 1, 4, 8, 5, 7]; IPinv_data = [4, 1, 3, 5, 7, 2, 8, 6]; EP_data = [4, 1, 2, 3, 2, 3, 4, 1]; P4_data = [2, 4, 3, 1]; SW_data = [5, 6, 7, 8, 1, 2, 3, 4]; #
SDES lookup tables
# S0_data = [[1, 0, 3, 2], [3, 2, 1, 0], [0, 2, 1, 3], [3, 1, 3, 2]]; S1_data = [[0, 1, 2, 3], [2, 0, 1, 3], [3, 0, 1, 0], [2, 1, 0, 3]]; def ApplyPermutation(X, permutation): r""" This function takes a permutation list (list of bit positions.) And outputs a bit list with the bits taken from X. """ # permute the list X l = len(permutation); return [X[permutation[j]-1] for j in xrange(l)]; def ApplySBox(X, SBox): r""" This function Applies the SDES SBox (by table look up """ r = 2X[0] + X[3]; c = 2X[1] + X[2]; o = SBox[r][c]; return [o & 2, o & 1]; #
Each of these functions uses ApplyPermutation
and a permutation list to perform an SDES
Expansion/Permutation
# def P10(X): return ApplyPermutation(X, P10_data); def P8(X): return ApplyPermutation(X, P8_data); def IP(X): return ApplyPermutation(X, IP_data); def IPinv(X): return ApplyPermutation(X, IPinv_data); def EP(X): return ApplyPermutation(X, EP_data); def EPinv(X): return ApplyPermutation(X, EPinv_data); def P4(X): return ApplyPermutation(X, P4_data); def SW(X): return ApplyPermutation(X, SW_data); def LS1(X): return ApplyPermutation(X, LS1_data); def LS2(X): return ApplyPermutation(X, LS2_data); #
These two functions perform the SBox substitutions
# def S0(X): return ApplySBox(X, S0_data); def S1(X): return ApplySBox(X, S1_data); def concatenate(left, right): r""" Joins to bit lists together. """ ret = [left[j] for j in xrange(len(left))]; ret.extend(right); return ret; def LeftHalfBits(block): r""" Returns the left half bits from block. """ l = len(block); return [block[j] for j in xrange(l/2)]; def RightHalfBits(block): r""" Returns the right half bits from block. """ l = len(block); return [block[j] for j in xrange(l/2, l)]; def XorBlock(block1, block2): r""" Xors two blocks together. """ l = len(block1); if (l != len(block2)): raise ValueError, "XorBlock arguments must be same length" return [(block1[j]+block2[j]) % 2 for j in xrange(l)]; def SDESKeySchedule(K): r""" Expands an SDES Key (bit list) into the two round keys. """ temp_K = P10(K); left_temp_K = LeftHalfBits(temp_K); right_temp_K = RightHalfBits(temp_K); K1left = LS1(left_temp_K); K1right = LS1(right_temp_K); K1temp = concatenate(K1left, K1right); K1 = P8(K1temp); K2left = LS2(K1left); K2right = LS2(K1right); K2temp = concatenate(K2left, K2right); K2 = P8(K2temp); return (K1, K2); def f_K(block, K): r""" Performs the f_K function supplied block and K. """ left_block = LeftHalfBits(block); right_block = RightHalfBits(block); temp_block1 = EP(right_block); temp_block2 = XorBlock(temp_block1, K); left_temp_block2 = LeftHalfBits(temp_block2); right_temp_block2 = RightHalfBits(temp_block2); S0_out = S0(left_temp_block2); S1_out = S1(right_temp_block2); temp_block3 = concatenate(S0_out, S1_out); temp_block4 = P4(temp_block3); temp_block5 = XorBlock(temp_block4, left_block); output_block = concatenate(temp_block5,right_block); return output_block; def SDESEncrypt(plaintext_block, K): r""" Performs a single SDES plaintext block encryption. (Given plaintext and key as bit lists.) """ (K1, K2) = SDESKeySchedule(K); temp_block1 = IP(plaintext_block); temp_block2 = f_K(temp_block1, K1); temp_block3 = SW(temp_block2); temp_block4 = f_K(temp_block3, K2); output_block = IPinv(temp_block4); return output_block;
///// in the part of f_K If I enter block = [0,1,0,1,0,1,1,0]; K = [0,0,0,0,1,1,1,0]; f_K(block, K)
the result is [0, 0, 0, 1, 0, 1, 1, 0] but from my calculation the result should be [ 0,0,0,0,0,1,1,0] could anyone help me to examine what is the problem please???
