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111 changes: 111 additions & 0 deletions ciphers/new.py
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'''
Created on Dec 27, 2016

@author: ralph
'''

from parser import stpcommands
from ciphers.cipher import AbstractCipher


class NewCipher(AbstractCipher):
"""
Represents the differential behaviour of PRESENT and can be used
to find differential characteristics for the given parameters.
"""

name = "new"

def getFormatString(self):
"""
Returns the print format.
"""
return ['S', 'P', 'w']

def createSTP(self, stp_filename, parameters):
"""
Creates an STP file to find a characteristic for PRESENT with
the given parameters.
"""

wordsize = parameters["wordsize"]
rounds = parameters["rounds"]
weight = parameters["sweight"]

if wordsize != 64:
print("Only wordsize of 64-bit supported.")
exit(1)

with open(stp_filename, 'w') as stp_file:
header = ("% Input File for STP\n% PRESENT w={}"
"rounds={}\n\n\n".format(wordsize, rounds))
stp_file.write(header)

# Setup variables
s = ["S{}".format(i) for i in range(rounds + 1)]
p = ["P{}".format(i) for i in range(rounds)]

# w = weight
w = ["w{}".format(i) for i in range(rounds)]

stpcommands.setupVariables(stp_file, s, wordsize)
stpcommands.setupVariables(stp_file, p, wordsize)
stpcommands.setupVariables(stp_file, w, wordsize)

stpcommands.setupWeightComputation(stp_file, weight, w, wordsize)

for i in range(rounds):
self.setupPresentRound(stp_file, s[i], p[i], s[i+1],
w[i], wordsize)

# No all zero characteristic
stpcommands.assertNonZero(stp_file, s, wordsize)

# Iterative characteristics only
# Input difference = Output difference
if parameters["iterative"]:
stpcommands.assertVariableValue(stp_file, s[0], s[rounds])

for key, value in parameters["fixedVariables"].items():
stpcommands.assertVariableValue(stp_file, key, value)

for char in parameters["blockedCharacteristics"]:
stpcommands.blockCharacteristic(stp_file, char, wordsize)

stpcommands.setupQuery(stp_file)

return

def setupPresentRound(self, stp_file, s_in, p, s_out, w, wordsize):
"""
Model for differential behaviour of one round PRESENT
"""
command = ""

#Permutation Layer
for i in range(16):
command += "ASSERT({0}[{1}:{1}] = {2}[{3}:{3}]);\n".format(p, i*4+0, s_out, i)
command += "ASSERT({0}[{1}:{1}] = {2}[{3}:{3}]);\n".format(p, i*4+1, s_out, i+16)
command += "ASSERT({0}[{1}:{1}] = {2}[{3}:{3}]);\n".format(p, i*4+2, s_out, i+32)
command += "ASSERT({0}[{1}:{1}] = {2}[{3}:{3}]);\n".format(p, i*4+3, s_out, i+48)

# Substitution Layer
present_sbox = [0xc, 5, 6, 0xb, 9, 0, 0xa, 0xd, 3, 0xe, 0xf, 8, 4, 7, 1, 2]
for i in range(16):
variables = ["{0}[{1}:{1}]".format(s_in, 4*i + 3),
"{0}[{1}:{1}]".format(s_in, 4*i + 2),
"{0}[{1}:{1}]".format(s_in, 4*i + 1),
"{0}[{1}:{1}]".format(s_in, 4*i + 0),
"{0}[{1}:{1}]".format(p, 4*i + 3),
"{0}[{1}:{1}]".format(p, 4*i + 2),
"{0}[{1}:{1}]".format(p, 4*i + 1),
"{0}[{1}:{1}]".format(p, 4*i + 0),
"{0}[{1}:{1}]".format(w, 4*i + 3),
"{0}[{1}:{1}]".format(w, 4*i + 2),
"{0}[{1}:{1}]".format(w, 4*i + 1),
"{0}[{1}:{1}]".format(w, 4*i + 0)]
command += stpcommands.add4bitSbox(present_sbox, variables)


stp_file.write(command)
return