Eugene Tan

s = [16, 42, 28, 3, 26, 0, 31, 46, 27, 14, 49, 62, 37, 56, 23, 6, 40, 48, 53, 8, 20, 25, 3, 1, 2, 63, 15, 34, 55, 21, 39, 57, 54, 45, 47, 13, 7, 44, 61, 9, 60, 32, 22, 29, 52, 19, 12, 50, 5, 51, 11, 18, 59, 41, 36, 30, 17, 38, 10, 4, 58, 43, 35, 24]

p = [24, 5, 15, 23, 14, 32, 19, 18, 26, 17, 6, 12, 34, 9, 8, 20, 28, 0, 2, 21, 29, 11, 33, 22, 30, 31, 1, 25, 3, 35, 16, 13, 27, 7, 10, 4]

key = 0

def sbox(x):
    '''S-box function'''
    return s[x]

def pbox(x):
    '''P-box function'''
    # if the texts are more than 32 bits,
    # then we have to use longs
    y = 0l

    # for each bit to be shuffled
    for i in range(len(p)):

        # if the original bit position
        # is a 1, then make the result
        # bit position have a 1
        if (x & (1l << i)) != 0:
            y = y ^ (1l << p[i])

    return y

def demux(x):
    '''Demultiplex, takes in 36-bit to six 6-bit values'''
    y = []
    for i in range(0, 6):
        y.append((x >> (i * 6)) & 0x3f)

    return y

def mux(x):
    '''Multiplex, takes in six 6-bit to 36-bit values'''
    y = 0l
    for i in range(0, 6):
        y = y ^ (x[i] << (i * 6))

    return y

def mix(p, k):
    '''Key mixing'''
    v = []
    key = demux(k)
    for i in range(0, 6):
        v.append(p[i] ^ key[i])

    return v

def round(p, k):
    '''Round function'''
    u = []

    # Calculate the S-boxes
    for x in demux(p):
        u.append(sbox(x))

    # Run through the P-box
    v = demux(pbox(mux(u)))

    # XOR in the key
    w = mix(v, k)

    # Glue back together, return
    return mux(w)

def encrypt(p, rounds):
    '''Encryption'''
    key = 0b111100001111000011111100001111000011
    x = p
    for i in range(rounds):
        x = round(x, key)

    return x

def apbox(x):
    y = 0l
    for i in range(len(p)):
        if (x & (1l << i)) != 0:
            pval = p.index(i)
            y = y ^ (1l << pval)
    return y

def asbox(x):
    return s.index(x)

def unround(c, k):
    '''Opposite of the round function'''
    x = demux(c)
    u = mix(x, k)
    v = demux(apbox(mux(u)))
    w = []
    for s in v:
        w.append(asbox(s))

    return mux(w)

def decrypt(c, rounds):
    '''Decryption function'''
    key = 0b111100001111000011111100001111000011
    x = c
    for i in range(rounds):
        x = unround(x, key)

    return x

if __name__ == '__main__':
    #import pdb
    #pdb.set_trace()
    plaintext = 0b111100001111000011110000111100001111
    ciphertext = encrypt(plaintext, 1)
    print 'plaintextA: ', plaintext
    print 'ciphertext: ', ciphertext
    print 'plaintextB: ', decrypt(ciphertext, 1)