def function(d,key):
data = xor(E(d),key)
s_result = ''
for index in range(1,9):
s = S[index]
B = data[(index-1)*6:(index-1)*6+6]
row = binary2decimal(B[0]+B[5])
col = binary2decimal(B[1:5])
s_result += decimal2binary(s[row][col],places=4)
return permute(s_result,P)
def decode_ECB(data,key):
keys = gen_keys(key)
decoded = ''
while len(data) > 0:
ip = permute(data[0:64],IP)
prev_L = ip[:32]
prev_R = ip[32:]
for x in range(16,0,-1):
L = prev_R
R = xor(prev_L,function(prev_R,keys[x-1]))
prev_L = L
prev_R = R
RL = R + L
next = permute(RL,IP_INVERSE)
#remove padding
if len(data) == 64:
last = next[56:]
for x in range(binary2decimal(last)):
next = next[0:len(next)-8]
decoded += next
data = data[64:]
return decoded
