util/design/lib/Present.py

# Python PRESENT implementation
# Version: 1.2
# Date: 01/27/2021
#
# Version 1.0: Original Version from https://github.com/doegox/python-cryptoplus
# Version 1.1: Minor modifications to run with Python >= 3.5
# Version 1.2: Remove string to int conversions
#
# =============================================================================
# Copyright (c) 2008 Christophe Oosterlynck <christophe.oosterlynck_AT_gmail.com>
#                    & NXP ( Philippe Teuwen <philippe.teuwen_AT_nxp.com> )
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
# =============================================================================

""" PRESENT block cipher implementation

USAGE EXAMPLE:
---------------
Importing:
-----------
>>> from pypresent import Present

Encrypting with a 80-bit key:
------------------------------
>>> key = 0x00000000000000000000
>>> plain = 0x0000000000000000
>>> cipher = Present(key, keylen=80)
>>> encrypted = cipher.encrypt(plain)
>>> hex(encrypted)
'0x5579c1387b228445'
>>> decrypted = cipher.decrypt(encrypted)
>>> hex(decrypted)
'0x0'

Encrypting with a 128-bit key:
-------------------------------
>>> key = 0x0123456789abcdef0123456789abcdef
>>> plain = 0x0123456789abcdef
>>> cipher = Present(key)
>>> encrypted = cipher.encrypt(plain)
>>> hex(encrypted)
'0xe9d28685e671dd6'
>>> decrypted = cipher.decrypt(encrypted)
>>> hex(decrypted)
'0x123456789abcdef'

fully based on standard specifications: http://www.crypto.ruhr-uni-bochum.de/imperia/md/content/texte/publications/conferences/present_ches2007.pdf
test vectors: http://www.crypto.ruhr-uni-bochum.de/imperia/md/content/texte/publications/conferences/slides/present_testvectors.zip
""" # noqa: E501 E261


class Present:
    def __init__(self, key, rounds=32, keylen=128):
        """Create a PRESENT cipher object

                key:    the key as an integer
                rounds: the number of rounds as an integer, 32 by default
                keylen: length of the key in bits
                """
        self.rounds = rounds
        if keylen == 80 and key < 2**80:
            self.roundkeys = generateRoundkeys80(key,
                                                 self.rounds)
        elif keylen == 128 and key < 2**128:
            self.roundkeys = generateRoundkeys128(key,
                                                  self.rounds)
        else:
            raise ValueError("keylen be 80 or 128")

    def encrypt(self, block):
        """Encrypt 1 block (8 bytes)

                Input:  plaintext block as raw string
                Output: ciphertext block as raw string
                """
        state = block
        for i in range(self.rounds - 1):
            state = addRoundKey(state, self.roundkeys[i])
            state = sBoxLayer(state)
            state = pLayer(state)
        cipher = addRoundKey(state, self.roundkeys[-1])
        return cipher

    def decrypt(self, block):
        """Decrypt 1 block (8 bytes)

                Input:  ciphertext block as raw string
                Output: plaintext block as raw string
                """
        state = block
        for i in range(self.rounds - 1):
            state = addRoundKey(state, self.roundkeys[-i - 1])
            state = pLayer_dec(state)
            state = sBoxLayer_dec(state)
        decipher = addRoundKey(state, self.roundkeys[0])
        return decipher

    def get_block_size(self):
        return 8


#        0   1   2   3   4   5   6   7   8   9   a   b   c   d   e   f
Sbox = [
    0xc, 0x5, 0x6, 0xb, 0x9, 0x0, 0xa, 0xd, 0x3, 0xe, 0xf, 0x8, 0x4, 0x7, 0x1,
    0x2
]
Sbox_inv = [Sbox.index(x) for x in range(16)]
PBox = [
    0, 16, 32, 48, 1, 17, 33, 49, 2, 18, 34, 50, 3, 19, 35, 51, 4, 20, 36, 52,
    5, 21, 37, 53, 6, 22, 38, 54, 7, 23, 39, 55, 8, 24, 40, 56, 9, 25, 41, 57,
    10, 26, 42, 58, 11, 27, 43, 59, 12, 28, 44, 60, 13, 29, 45, 61, 14, 30, 46,
    62, 15, 31, 47, 63
]
PBox_inv = [PBox.index(x) for x in range(64)]


def generateRoundkeys80(key, rounds):
    """Generate the roundkeys for a 80-bit key

        Input:
                key:    the key as a 80-bit integer
                rounds: the number of rounds as an integer
        Output: list of 64-bit roundkeys as integers"""
    roundkeys = []
    for i in range(1, rounds + 1):  # (K1 ... K32)
        # rawkey: used in comments to show what happens at bitlevel
        # rawKey[0:64]
        roundkeys.append(key >> 16)
        # 1. Shift
        # rawKey[19:len(rawKey)]+rawKey[0:19]
        key = ((key & (2**19 - 1)) << 61) + (key >> 19)
        # 2. SBox
        # rawKey[76:80] = S(rawKey[76:80])
        key = (Sbox[key >> 76] << 76) + (key & (2**76 - 1))
        # 3. Salt
        # rawKey[15:20] ^ i
        key ^= i << 15
    return roundkeys


def generateRoundkeys128(key, rounds):
    """Generate the roundkeys for a 128-bit key

        Input:
                key:    the key as a 128-bit integer
                rounds: the number of rounds as an integer
        Output: list of 64-bit roundkeys as integers"""
    roundkeys = []
    for i in range(1, rounds + 1):  # (K1 ... K32)
        # rawkey: used in comments to show what happens at bitlevel
        roundkeys.append(key >> 64)
        # 1. Shift
        key = ((key & (2**67 - 1)) << 61) + (key >> 67)
        # 2. SBox
        key = (Sbox[key >> 124] << 124) + (Sbox[
            (key >> 120) & 0xF] << 120) + (key & (2**120 - 1))
        # 3. Salt
        # rawKey[62:67] ^ i
        key ^= i << 62
    return roundkeys


def addRoundKey(state, roundkey):
    return state ^ roundkey


def sBoxLayer(state):
    """SBox function for encryption

        Input:  64-bit integer
        Output: 64-bit integer"""

    output = 0
    for i in range(16):
        output += Sbox[(state >> (i * 4)) & 0xF] << (i * 4)
    return output


def sBoxLayer_dec(state):
    """Inverse SBox function for decryption

        Input:  64-bit integer
        Output: 64-bit integer"""
    output = 0
    for i in range(16):
        output += Sbox_inv[(state >> (i * 4)) & 0xF] << (i * 4)
    return output


def pLayer(state):
    """Permutation layer for encryption

        Input:  64-bit integer
        Output: 64-bit integer"""
    output = 0
    for i in range(64):
        output += ((state >> i) & 0x01) << PBox[i]
    return output


def pLayer_dec(state):
    """Permutation layer for decryption

        Input:  64-bit integer
        Output: 64-bit integer"""
    output = 0
    for i in range(64):
        output += ((state >> i) & 0x01) << PBox_inv[i]
    return output


def _test():
    import doctest
    doctest.testmod()


if __name__ == "__main__":
    _test()