[IS] DES Cryptosystem

__author__ = 'rezoh'

class des():
    # Permutation and translation tables for DES
    __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
    ]

    # number left rotations of pc1
    __left_rotations = [
        1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
    ]

    # permuted choice key (table 2)
    __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
    ]

    # initial permutation IP
    __ip = [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
    ]

    # Expansion table for turning 32 bit blocks into 48 bits
    __expansion_table = [
        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
    ]

    # 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],
    ]


    # 32-bit permutation function P used on the output of the S-boxes
    __p = [
        15, 6, 19, 20, 28, 11,
        27, 16, 0, 14, 22, 25,
        4, 17, 30, 9, 1, 7,
        23, 13, 31, 26, 2, 8,
        18, 12, 29, 5, 21, 10,
        3, 24
    ]

    # final permutation IP^-1
    __fp = [
        39, 7, 47, 15, 55, 23, 63, 31,
        38, 6, 46, 14, 54, 22, 62, 30,
        37, 5, 45, 13, 53, 21, 61, 29,
        36, 4, 44, 12, 52, 20, 60, 28,
        35, 3, 43, 11, 51, 19, 59, 27,
        34, 2, 42, 10, 50, 18, 58, 26,
        33, 1, 41, 9, 49, 17, 57, 25,
        32, 0, 40, 8, 48, 16, 56, 24
    ]

    # Type of crypting being done
    ENCRYPT = 0x00
    DECRYPT = 0x01

    # Initialisation
    def __init__(self, key):
        # Sanity checking of arguments.
        self.block_size = 8 #block size
        if len(key) != 8:
            raise ValueError("Invalid DES key size. Key must be exactly 8 bytes long.")

        self.key_size = 8

        self.L = []
        self.R = []
        self.Kn = [[0] * 48] * 16  # 16 48-bit keys (K1 - K16)
        self.final = []

        self.setKey(key)

    def setKey(self, key):
        self.__key = key
        self.__create_sub_keys()


    def getKey(self):
        return self.__key


    def _padData(self, data):
        # Pad data depending on the mode

        pad_len = 8 - (len(data) % self.block_size)
        data += pad_len * chr(pad_len)

        return data

    def _unpadData(self, data,):
        # Unpad data depending on the mode.
        if not data:
            return data

        pad_len = ord(data[-1])
        data = data[:-pad_len]

        return data

    def __String_to_BitList(self, data):
        data = [ord(c) for c in data]
        l = len(data) * 8
        result = [0] * l
        pos = 0
        for ch in data:
            i = 7
            while i >= 0:
                if ch & (1 << i) != 0:
                    result[pos] = 1
                else:
                    result[pos] = 0
                pos += 1
                i -= 1

        return result

    def __BitList_to_String(self, data):
        result = []
        pos = 0
        c = 0
        while pos < len(data):
            c += data[pos] << (7 - (pos % 8))
            if (pos % 8) == 7:
                result.append(c)
                c = 0
            pos += 1

        return ''.join([chr(c) for c in result])

    def __permutate(self, table, block):
        """Permutate this block with the specified table"""
        return list(map(lambda x: block[x], table))

    # Transform the secret key, so that it is ready for data processing
    # Create the 16 subkeys, K[1] - K[16]
    def __create_sub_keys(self):
        """Create the 16 subkeys K[1] to K[16] from the given key"""
        key = self.__permutate(des.__pc1, self.__String_to_BitList(self.getKey()))
        i = 0
        # Split into Left and Right sections
        self.L = key[:28]
        self.R = key[28:]
        while i < 16:
            j = 0
            # Perform circular left shifts
            while j < des.__left_rotations[i]:
                self.L.append(self.L[0])
                del self.L[0]

                self.R.append(self.R[0])
                del self.R[0]

                j += 1

            # Create one of the 16 subkeys through pc2 permutation
            self.Kn[i] = self.__permutate(des.__pc2, self.L + self.R)

            i += 1


    def __des_crypt(self, block, crypt_type):
        """Crypt the block bit-manipulation"""
        block = self.__permutate(des.__ip, block)
        self.L = block[:32]
        self.R = block[32:]

        # Encryption starts from Kn[1] through to Kn[16]
        if crypt_type == des.ENCRYPT:
            iteration = 0
            iteration_adjustment = 1
        # Decryption starts from Kn[16] down to Kn[1]
        else:
            iteration = 15
            iteration_adjustment = -1

        #crypt loop
        i = 0
        while i < 16:
            tempR = self.R[:]
            #first permutation
            self.R = self.__permutate(des.__expansion_table, self.R)
            #extended E E(R-1)
            self.R = list(map(lambda x, y: x ^ y, self.R, self.Kn[iteration]))
            #divide for 8 blocks
            B = [self.R[:6], self.R[6:12], self.R[12:18], self.R[18:24], self.R[24:30], self.R[30:36], self.R[36:42],
                 self.R[42:]]
            j = 0
            Bn = [0] * 32
            pos = 0
            #transform B(i) by S-permutation
            while j < 8:
                m = (B[j][0] << 1) + B[j][5]
                n = (B[j][1] << 3) + (B[j][2] << 2) + (B[j][3] << 1) + B[j][4]

                v = des.__sbox[j][(m << 4) + n]

                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
            self.R = self.__permutate(des.__p, Bn)
            #swap blocks
            self.R = list(map(lambda x, y: x ^ y, self.R, self.L))
            self.L = tempR

            i += 1
            iteration += iteration_adjustment

        #end permutate by P
        self.final = self.__permutate(des.__fp, self.R + self.L)
        return self.final


    # Data to be encrypted/decrypted
    def crypt(self, data, crypt_type):
        """Crypt the data in blocks, running it through des_crypt()"""
        i = 0
        dict = {}
        result = []
        #devide text on blocks and encrypt
        while i < len(data):

            block = self.__String_to_BitList(data[i:i + 8])

            processed_block = self.__des_crypt(block, crypt_type)

            result.append(self.__BitList_to_String(processed_block))
            i += 8

        return ''.join(result)


    def encrypt(self, data):
        data = data
        data = self._padData(data)
        return self.crypt(data, des.ENCRYPT)


    def decrypt(self, data):
        data = data
        data = self.crypt(data, des.DECRYPT)
        return self._unpadData(data)


decr = des("KEYKEYAK")
d = decr.encrypt("OMG Im fuckin pretty good man!!")
en = decr.decrypt(d)
print(en)