Subversion Repositories Code-Repo

# S-box lookup table calculated from the field F_{2^8} = Z_2[x]/x^8+x^4+x^3+x+1
                #  0    1    2    3    4    5    6    7    8    9    A    B    C    D    E    F
s_box = [[0x63,0x7C,0x77,0x7B,0xF2,0x6B,0x6F,0xC5,0x30,0x01,0x67,0x2B,0xFE,0xD7,0xAB,0x76],#0
                 [0XCA,0X82,0XC9,0X7D,0XFA,0X59,0X47,0XF0,0XAD,0XD4,0XA2,0XAF,0X9C,0XA4,0X72,0XC0],#1
                 [0XB7,0XFD,0X93,0X26,0X36,0X3F,0XF7,0XCC,0X34,0XA5,0XE5,0XF1,0X71,0XD8,0X31,0X15],#1
                 [0x04,0xC7,0x23,0xC3,0x18,0x96,0x05,0x9A,0x07,0x12,0x80,0xE2,0xEB,0x27,0xB2,0x75],#3
                 [0x09,0x83,0x2C,0x1A,0x1B,0x6E,0x5A,0xA0,0x52,0x3B,0xD6,0xB3,0x29,0xE3,0x2F,0x84],#4
                 [0x53,0xD1,0x00,0xED,0x20,0xFC,0xB1,0x5B,0x6A,0xCB,0xBE,0x39,0x4A,0x4C,0x58,0xCF],#5
                 [0xD0,0xEF,0xAA,0xFB,0x43,0x4D,0x33,0x85,0x45,0xF9,0x02,0x7F,0x50,0x3C,0x9F,0xA8],#6
                 [0x51,0xA3,0x40,0x8F,0x92,0x9D,0x38,0xF5,0xBC,0xB6,0xDA,0x21,0x10,0xFF,0xF3,0xD2],#7
                 [0xCD,0x0C,0x13,0xEC,0x5F,0x97,0x44,0x17,0xC4,0xA7,0x7E,0x3D,0x64,0x5D,0x19,0x73],#8
                 [0x60,0x81,0x4F,0xDC,0x22,0x2A,0x90,0x88,0x46,0xEE,0xB8,0x14,0xDE,0x5E,0x0B,0xDB],#9
                 [0xE0,0x32,0x3A,0x0A,0x49,0x06,0x24,0x5C,0xC2,0xD3,0xAC,0x62,0x91,0x95,0xE4,0x79],#A
                 [0xE7,0xC8,0x37,0x6D,0x8D,0xD5,0x4E,0xA9,0x6C,0x56,0xF4,0xEA,0x65,0x7A,0xAE,0x08],#B
                 [0xBA,0x78,0x25,0x2E,0x1C,0xA6,0xB4,0xC6,0xE8,0xDD,0x74,0x1F,0x4B,0xBD,0x8B,0x8A],#C
                 [0x70,0x3E,0xB5,0x66,0x48,0x03,0xF6,0x0E,0x61,0x35,0x57,0xB9,0x86,0xC1,0x1D,0x9E],#D
                 [0xE1,0xF8,0x98,0x11,0x69,0xD9,0x8E,0x94,0x9B,0x1E,0x87,0xE9,0xCE,0x55,0x28,0xDF],#E
                 [0x8C,0xA1,0x89,0x0D,0xBF,0xE6,0x42,0x68,0x41,0x99,0x2D,0x0F,0xB0,0x54,0xBB,0x16]]#F

# Key expansion lookup table
RCon = [[0x01,0x00,0x00,0x00],[0x02,0x00,0x00,0x00],[0x04,0x00,0x00,0x00],[0x08,0x00,0x00,0x00],
                [0x10,0x00,0x00,0x00],[0x20,0x00,0x00,0x00],[0x40,0x00,0x00,0x00],[0x80,0x00,0x00,0x00],
                [0x1B,0x00,0x00,0x00],[0x36,0x00,0x00,0x00]]

# Encryption key
encryption_key = [0x2B,0x7E,0x15,0x16,0x28,0xAE,0xD2,0xA6,0xAB,0xF7,0x15,0x88,0x09,0xCF,0x4F,0x3C]

# Input plaintext
plaintext = [0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF]

def RotWord(byte_array):
        '''Takes a list of bytes and cyclic left shifts it by one.'''
        byte_array.append(byte_array.pop(0))
        return byte_array

def SubBytes(byte_array):
        '''Substitutes each byte in the given list with the value in the s-box.'''
        for i in range(len(byte_array)):
                byte_array[i] = s_box[(byte_array[i]&0xF0)>>4][byte_array[i]&0xF]
        return byte_array

def XorBytes(byte_array,input):
        '''XORs two byte arrays and returns the result.'''
        for i in range(len(byte_array)):
                byte_array[i] ^= input[i]
        return byte_array

def ShiftRows(byte_array):
        '''Shifts the second row left by one, the third row by two, and the fourth row by three.'''
        # Shift second row
        temp = byte_array[1]
        byte_array[1] = byte_array[5]
        byte_array[5] = byte_array[9]
        byte_array[9] = byte_array[13]
        byte_array[13] = temp
        # Shift third row
        temp = byte_array[2]
        byte_array[2] = byte_array[10]
        byte_array[10] = temp
        temp = byte_array[6]
        byte_array[6] = byte_array[14]
        byte_array[14] = temp
        # Shift fourth row
        temp = byte_array[3]
        byte_array[3] = byte_array[15]
        byte_array[15] = byte_array[11]
        byte_array[11] = byte_array[7]
        byte_array[7] = temp
        return byte_array

def MC_Mul(byte,mul):
        '''Helper function for MixColumns'''
        if mul == 2:
                byte <<= 1
                if byte > 0xFF:
                        byte ^= 0x11B
        elif mul == 3:
                byte = (byte<<1)^byte
                if byte > 0xFF:
                        byte ^= 0x11B
        return byte

def MixColumns(byte_array):
        '''Mixes each column by multiplying it with a certain matrix of elements of the field F_{2^8}.'''
        ret = []
        for i in [0,4,8,12]:
                ret.append((MC_Mul(byte_array[i],2) ^ MC_Mul(byte_array[i+1],3) ^ byte_array[i+2] ^ byte_array[i+3])&0xFF)
                ret.append((byte_array[i] ^ MC_Mul(byte_array[i+1],2) ^ MC_Mul(byte_array[i+2],3) ^ byte_array[i+3])&0xFF)
                ret.append((byte_array[i] ^ byte_array[i+1] ^ MC_Mul(byte_array[i+2],2) ^ MC_Mul(byte_array[i+3],3))&0xFF)
                ret.append((MC_Mul(byte_array[i],3) ^ byte_array[i+1] ^ byte_array[i+2] ^ MC_Mul(byte_array[i+3],2))&0xFF)
        return ret

def KeyExpansion(key):
        '''Computes and returns the expansion key for a given encryption key.'''
        expanded_key = []
        for i in range(4):
                expanded_key.append([key[4*i],key[4*i+1],key[4*i+2],key[4*i+3]])
        for i in range(4,44):
                temp = list(expanded_key[i-1])
                if i % 4 == 0:
                        temp = XorBytes(SubBytes(RotWord(temp)),RCon[(i/4)-1])
                expanded_key.append(XorBytes(list(expanded_key[i-4]),temp))
        return expanded_key

def RoundKey(expansion_key,round):
        '''Computes and returns the round key given the expansion key.'''
        round_key = []
        for i in range(4):
                for j in range(4):
                        round_key.append(expansion_key[4*round+i][j])
        return round_key

if __name__ == '__main__':
        # Calculate and print out the round keys
        expansion_key = KeyExpansion(encryption_key)
        for i in range(11):
                round_key = RoundKey(expansion_key, i)
                print "Round Key %d:" % i,
                for j in range(16):
                        print "%02X" % round_key[j],
                print 
        print

        # Print out round 0 info
        state = list(plaintext)
        print "Initial state = plaintext:\t",
        for i in range(16):
                print "%02X" % state[i],
        print

        print "Round 0 (Add Round Key 0):\t",
        state = XorBytes(state, RoundKey(expansion_key, 0))
        for i in range(16):
                print "%02X" % state[i],
        print "\n"

        # Print out the results of each round
        for i in range(1,10):
                print "Round %d (SubBytes):\t\t\t" % i,
                state = SubBytes(state)
                for j in range(16):
                        print "%02X" % state[j],
                print

                print "Round %d (ShiftRows):\t\t" % i,
                state = ShiftRows(state)
                for j in range(16):
                        print "%02X" % state[j],
                print

                print "Round %d (MixColumns):\t\t" % i,
                state = MixColumns(state)
                for j in range(16):
                        print "%02X" % state[j],
                print

                print "Round %d (Add Round Key %d):\t" % (i,i),
                state = XorBytes(state, RoundKey(expansion_key, i))
                for j in range(16):
                        print "%02X" % state[j],
                print "\n"

        # Print out the results for the final round
        print "Round 10 (SubBytes):\t\t",
        state = SubBytes(state)
        for j in range(16):
                print "%02X" % state[j],
        print

        print "Round 10 (ShiftRows):\t\t",
        state = ShiftRows(state)
        for j in range(16):
                print "%02X" % state[j],
        print

        print "Round 10 (Add Round Key 10):",
        state = XorBytes(state, RoundKey(expansion_key, 10))
        for j in range(16):
                print "%02X" % state[j],
        print "\n"

        # Print the ciphertext
        print "Ciphertext:\t\t\t",
        for j in range(16):
                print "%02X" % state[j],
        print