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# Implementation of the Lilliput-AE tweakable block cipher.
#
# Authors, hereby denoted as "the implementer":
# Kévin Le Gouguec,
# Léo Reynaud
# 2019.
#
# For more information, feedback or questions, refer to our website:
# https://paclido.fr/lilliput-ae
#
# To the extent possible under law, the implementer has waived all copyright
# and related or neighboring rights to the source code in this file.
# http://creativecommons.org/publicdomain/zero/1.0/
"""Lilliput-TBC tweakable block cipher.
This module provides functions to encrypt and decrypt blocks of 128 bits.
"""
from .constants import BLOCK_BYTES, Sbox
from .multiplications import ALPHAS
_permutation = [14, 11, 12, 10, 8, 9, 13, 15, 3, 1, 4, 5, 6, 0, 2, 7]
_permutationInv = [13, 9, 14, 8, 10, 11, 12, 15, 4, 5, 3, 1, 2, 6 ,0 ,7]
################################################################################
def _BuildTweakey(tweak, key):
return tweak+key
#############################
def _Lane(TK, j):
return TK[j*8:(j+1)*8]
def _RoundTweakeySchedule(tweakey):
p = len(tweakey)//8
multiplied_lanes = (
ALPHAS[j](_Lane(tweakey, j)) for j in range(p)
)
return [byte for lane in multiplied_lanes for byte in lane]
def _SubTweakeyExtract(tweakey, Ci):
RTKi = [0]*8
for j, byte in enumerate(tweakey):
RTKi[j%8] ^= byte
RTKi[0] ^= Ci
return RTKi
def _TweakeyScheduleWhole(tweakey, r):
# Store the initial tweakey in TKs[0], and the corresponding round tweakey
# in RTKs[0].
TKs = [tweakey]
RTKs = [_SubTweakeyExtract(TKs[0], 0)]
for i in range(1, r):
TKs.append(_RoundTweakeySchedule(TKs[i-1]))
RTKs.append(_SubTweakeyExtract(TKs[i], i))
return RTKs
################################################################################
def _NonLinearLayer(state, subtweakey):
variables_xored = [0 for byte in range(0, 8)]
for byte in range(0,8):
variables_xored[byte] = state[byte] ^ subtweakey[byte]
variables_sboxed = [0 for byte in range(0, 8)]
for byte in range(0, 8):
variables_sboxed[byte] = Sbox[variables_xored[byte]]
state_output = [0 for byte in range(0, BLOCK_BYTES)]
for byte in range(0,BLOCK_BYTES):
state_output[byte] = state[byte]
for byte in range(0, 8):
state_output[15 - byte] ^= variables_sboxed[byte]
return state_output
def _LinearLayer(state):
state_output = [0 for byte in range(0, BLOCK_BYTES)]
for byte in range(0, BLOCK_BYTES):
state_output[byte] = state[byte]
for byte in range(1, 8):
state_output[15] ^= state[byte]
for byte in range(9, 15):
state_output[byte] ^= state[7]
return state_output
def _PermutationLayerEnc(state):
state_output = [0 for byte in range(0, BLOCK_BYTES)]
for byte in range(0, BLOCK_BYTES):
state_output[byte] = state[_permutation[byte]]
return state_output
def _PermutationLayerDec(state):
state_output = [0 for byte in range(0, BLOCK_BYTES)]
for byte in range(0, BLOCK_BYTES):
state_output[byte] = state[_permutationInv[byte]]
return state_output
def _OneRoundEGFNEnc(state, subtweakey):
state_non_linear = _NonLinearLayer(state, subtweakey)
state_linear = _LinearLayer(state_non_linear)
state_permutation = _PermutationLayerEnc(state_linear)
return state_permutation
def _LastRoundEGFN(state, subtweakey):
state_non_linear = _NonLinearLayer(state, subtweakey)
state_linear = _LinearLayer(state_non_linear)
return state_linear
def _OneRoundEGFNDec(state, subtweakey):
state_non_linear = _NonLinearLayer(state, subtweakey)
state_linear = _LinearLayer(state_non_linear)
state_permutation = _PermutationLayerDec(state_linear)
return state_permutation
def _Rounds(key_bytes):
rounds = {
128: 32,
192: 36,
256: 42
}
return rounds[key_bytes*8]
################################################################################
def encrypt(tweak, key, message):
r = _Rounds(len(key))
tweakey = _BuildTweakey(tweak, key)
RTKs = _TweakeyScheduleWhole(tweakey, r)
state = [0 for byte in range(0, BLOCK_BYTES)]
for byte in range(0, BLOCK_BYTES):
state[byte] = message[byte]
for i in range(0, r-1):
state_output = _OneRoundEGFNEnc(state, RTKs[i])
for byte in range(0, BLOCK_BYTES):
state[byte] = state_output[byte]
state_output = _LastRoundEGFN(state, RTKs[r-1])
return state_output
def decrypt(tweak, key, cipher):
r = _Rounds(len(key))
tweakey = _BuildTweakey(tweak, key)
RTKs = _TweakeyScheduleWhole(tweakey, r)
state = [0 for byte in range(0, BLOCK_BYTES)]
for byte in range(0, BLOCK_BYTES):
state[byte] = cipher[byte]
for i in range(0, r-1):
state_output = _OneRoundEGFNDec(state, RTKs[r-i-1])
for byte in range(0, BLOCK_BYTES):
state[byte] = state_output[byte]
state_output = _LastRoundEGFN(state, RTKs[0])
return state_output
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