aes.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

""" CONSTANTS """
sbox = [    0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5, 0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76,
            0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0, 0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0,
            0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC, 0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15,
            0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A, 0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75,
            0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0, 0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84,
            0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B, 0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF,
            0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85, 0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8,
            0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5, 0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2,
            0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17, 0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73,
            0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88, 0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB,
            0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C, 0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79,
            0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9, 0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08,
            0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6, 0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A,
            0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E, 0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E,
            0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94, 0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF,
            0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68, 0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16]

rcon = [[0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80,0x1b,0x36],
        [0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00],
        [0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00],
        [0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00]]


class libutils:

    """ n       ->  nº of column to change
        block   ->  block 4x4 (key)
        column  ->  block 4x1 (RotWord)
    """
    ## Example of use libutils._changecolumn(antKey,[0x09,0xcf,0x4f,0x3c],0) ##
    @staticmethod
    def _changecolumn(block,column,n):
        for i in xrange(4):
            block[i][n] = column[i]
        return block

    ## PRECONDITION n<=col(block) ##
    @staticmethod
    def _getcolumn(block,n):
        return [block[i][n] for i in xrange(4)]

    @staticmethod
    def _getallcolumns(block):
        return [libutils._getcolumn(block,n) for n in xrange(len(block))]

    @staticmethod
    ## Change first byte at last byte of the column ##
    def _rotword(column):
        tmp = column[0]
        for i in xrange(len(column)-1):
            column[i] = column[i+1]
        column[len(column)-1] = tmp
        return column

    @staticmethod
    ## Make SubBytes process ##
    def _subbytes(column):
        return [sbox[i] for i in column]

    @staticmethod
    ## Xor 3 columns -> key schedule col1 xor col2 xor Rcon[i] ##
    ## PRECONDITION len(col1) == len(col2) == len(col3) ##
    def _xor3columns(col1,col2,col3):
        return [col1[i] ^ col2[i] ^ col3[i] for i in xrange(len(col1))]

    @staticmethod
    ## Xor 2 columns ##
    ## PRECONDITION len(col1) == len(col2) ##
    def _xor2columns(col1,col2):
        return [col1[i] ^ col2[i] for i in xrange(len(col1))]

    @staticmethod
    ## Build matrix by columns ##
    def _buildmatrixcol(*args):
        matrix = [[0x00]*len(args) for i in xrange(len(args))]
        for i in xrange(len(args)):
            libutils._changecolumn(matrix,args[i],i)
        return matrix



class cipheralgorithms:


    @staticmethod
    def _aes(*args):
        cipherText = [[0x38,0x88,0x31,0xe0],[0x43,0x5a,0x31,0x37],[0xf6,0x30,0x98,0x07],[0xa8,0x8d,0xa2,0x34]]
        cipherKey  = [[0x2b,0x28,0xab,0x09],[0x7e,0xae,0xf7,0xcf],[0x15,0xd2,0x15,0x4f],[0x16,0xa6,0x88,0x3c]]
        if args != ():
            cipherText = args[0]
            if len(args) == 2:
                cipherKey  = args[1]
        # Key schedule
        cipherKey  = cipheralgorithms.__keyschedule(cipherKey)


    @staticmethod
    def __keyschedule(cipherKey):

        antKey,schedule,actCol,i,actPos,actPosRcon = cipherKey,[],None,0,0,0
        ## Fill schedule 4x40 ##
        schedule = [[0x00]*44 for i in xrange(4)]
        ## Set initial status of schedule ##
        for col in libutils._getallcolumns(antKey):
            schedule = libutils._changecolumn(schedule,col,actPos)
            actPos += 1
        for i in xrange(40):
            ## Take ant col ##
            actCol = libutils._getcolumn(schedule,actPos-1)
            ## If is word in multiple of 4, rotword and subbytes ##
            if(actPos%4==0):
                actCol = libutils._rotword(actCol)
                actCol = libutils._subbytes(actCol)
                actCol = libutils._xor3columns(libutils._getcolumn(schedule,actPos-4),actCol,libutils._getcolumn(rcon,actPosRcon))
                actPosRcon += 1
            else:
                actCol = libutils._xor2columns(libutils._getcolumn(schedule,actPos-4),actCol)
            libutils._changecolumn(schedule,actCol,actPos)
            actPos += 1
        return libutils._buildmatrixcol(libutils._getcolumn(schedule,40),libutils._getcolumn(schedule,41),
                                        libutils._getcolumn(schedule,42),libutils._getcolumn(schedule,43))


if __name__ == "__main__":
    # Se puede llamar con 1 o 2 parámetros cipherText y/o cipherKey
    cipheralgorithms._aes()