index out of range in DES python

Question

I am really sorry for the long program I am complaining about it here, I am just trying to make up my own DES encryption code using python with the little knowledge I have. So I have written the following code: It returned an error saying :" m = (B[j][0] << 1) + B[j][5] IndexError: bitarray index out of range". How can I solve that?

from bitarray import bitarray
    iptable=[57, 49, 41, 33, 25, 17, 9,  1,
            59, 51, 43, 35, 27, 19, 11, 3,
            61, 53, 45, 37, 29, 21, 13, 5,
            63, 55, 47, 39, 31, 23, 15, 7,
            56, 48, 40, 32, 24, 16, 8,  0,
            58, 50, 42, 34, 26, 18, 10, 2,
            60, 52, 44, 36, 28, 20, 12, 4,
            62, 54, 46, 38, 30, 22, 14, 6
        ]
    pc1=[56, 48, 40, 32, 24, 16,  8,
              0, 57, 49, 41, 33, 25, 17,
              9,  1, 58, 50, 42, 34, 26,
             18, 10,  2, 59, 51, 43, 35,
             62, 54, 46, 38, 30, 22, 14,
              6, 61, 53, 45, 37, 29, 21,
             13,  5, 60, 52, 44, 36, 28,
             20, 12,  4, 27, 19, 11,  3
        ]
    expTable=[31,  0,  1,  2,  3,  4,
             3,  4,  5,  6,  7,  8,
             7,  8,  9, 10, 11, 12,
            11, 12, 13, 14, 15, 16,
            15, 16, 17, 18, 19, 20,
            19, 20, 21, 22, 23, 24,
            23, 24, 25, 26, 27, 28,
            27, 28, 29, 30, 31,  0]
    pc2 = [13, 16, 10, 23,  0,  4,
             2, 27, 14,  5, 20,  9,
            22, 18, 11,  3, 25,  7,
            15,  6, 26, 19, 12,  1,
            40, 51, 30, 36, 46, 54,
            29, 39, 50, 44, 32, 47,
            43, 48, 38, 55, 33, 52,
            45, 41, 49, 35, 28, 31] 
    # The (in)famous S-boxes
    __sbox = [
            # S1
            [14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
             0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
             4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
             15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13],

            # S2
            [15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,
             3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
             0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
             13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9],

            # S3
            [10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,
             13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
             13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
             1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12],

            # S4
            [7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,
             13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
             10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
             3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14],

            # S5
            [2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,
             14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
             4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
             11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3],

            # S6
            [12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,
             10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
             9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
             4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13],

            # S7
            [4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,
             13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
             1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
             6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12],

            # S8
            [13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,
             1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
             7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
             2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11],
        ]
    msg= bitarray(endian='little')
    msg.frombytes(b'ABCDEFGH')
    perm = bitarray(endian='little')
    key= bitarray(endian='little')
    key.frombytes(b'FFQQSSMM')
    keyPc1 = bitarray(endian='little')
    keyPc2 = bitarray(endian='little')
    exp = bitarray(endian='little')
    for z in pc1:
        keyPc1.append(key[z])
    c0 = keyPc1[0:28]
    d0 = keyPc1[28:]
    key0 = c0 + d0
    #permutation of key
    for k in pc2:
        keyPc2.append(key0[k])
    #permutation of message
    for x in iptable:
        perm.append(msg[x])
    l1 = perm[0:32]
    r1 = perm[32:]
    #Expansion of R
    for y in expTable:
        exp.append(r1[y])
    #XORing R & key
    xor_rk = keyPc2 ^ exp
    #Working with S-boxes!
    B = [xor_rk[0:6], xor_rk[6:14], xor_rk[14:20], xor_rk[20:26], xor_rk[26:32], xor_rk[32:38], xor_rk[38:42], xor_rk[42:47]]
    j = 0
    Bn = [0] * 32
    pos = 0
    while j < 8:
        # Work out the offsets
        m = (B[j][0] << 1) + B[j][5]
        n = (B[j][1] << 3) + (B[j][2] << 2) + (B[j][3] << 1) + B[j][4]
        # Find the permutation value
        v = __sbox[j][(m << 4) + n]
        # Turn value into bits, add it to result: Bn
        Bn[pos] = (v & 8) >> 3
        Bn[pos + 1] = (v & 4) >> 2
        Bn[pos + 2] = (v & 2) >> 1
        Bn[pos + 3] = v & 1
        pos += 4
        j += 1
    f = Bn[0] + Bn[1] + Bn[2] + Bn[3] + Bn[4] +Bn[5] + Bn[6] +Bn[7]
    xor_lf = l ^ f

Answer 1

Not all parts of your B list are the same length. For example, this part:

xor_rk[38:42]

has a length of 4, so you can't get the 5th element of that. Is it supposed to have a length of 4? Or did you mean to count by sixes and screw up?