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# coding=utf8
# =============================================================================
# Python PRIDE implementation
# Version: 1.0
# Date: 23/04/2015
#
# =============================================================================
#
# Python implementation of the PRIDE cipher
# Copyright (C) 2015 Camil Staps (info@camilstaps.nl)
#
# Some general implementation ideas were taken from Cristophe Osterlynck and
# Philippe Teuwen's PRESENT implementation:
# http://www.lightweightcrypto.org/downloads/implementations/pypresent.py
#
# =============================================================================
#
# PRIDE is a modern (2014) lightweight block cipher optimized for 8-bit
# microcontrollers, that "significantly outperforms all existing block ciphers
# of similar key-sizes, with the exception of SIMON and SPECK". Its design
# rationale is described in Block Ciphers -- Focus On The Linear Layer (feat.
# PRIDE); Martin R. Albrecht, Benedikt Driessen, Elif Bilge Kavun, Gregor
# Leander, Christof Paar, Tolga Yalçın: https://eprint.iacr.org/2014/453
#
# =============================================================================
"""
PRIDE block cipher implementation
USAGE EXAMPLE:
---------------
Importing:
-----------
>>> from pypride import Pride
Create a Pride object:
-----------------------
>>> key = "00000000000000000000000000000000".decode('hex')
>>> cipher = Pride(key)
Encryption:
------------
>>> plain = "0000000000000000".decode('hex')
>>> encrypted = cipher.encrypt(plain)
>>> encrypted.encode('hex')
'82b4109fcc70bd1f'
Decryption:
------------
>>> decrypted = cipher.decrypt(encrypted)
>>> decrypted.encode('hex')
'0000000000000000'
This implementation is fully based on the report PRIDE was presented in (https://eprint.iacr.org/2014/453; specifically section 5.4).
Test vectors can be found in test-vectors.py and were taken from appendix J of that paper.
"""
class Pride:
def __init__(self,key):
"""Create a PRIDE cipher object
Input: the key as a 128-bit raw string"""
if len(key) != 16:
raise ValueError, "Key must be a 128-bit raw string"
self.whitening_key = string2number(key[:8])
self.roundkeys = [roundKey(key[8:], i) for i in xrange(0,21)]
def encrypt(self,block):
"""Encrypt 1 block (8 bytes)
Input: plaintext block as raw string
Output: ciphertext block as raw string"""
state = string2number(block)
# Initial permutation & pre-whitening
state = pLayer_dec(state)
state = addRoundKey(state, self.whitening_key)
# 19 rounds R
for i in xrange (1,20):
state = addRoundKey(state, self.roundkeys[i])
state = sBoxLayer(state)
state = lLayer(state)
# Last round R'
state = addRoundKey(state, self.roundkeys[20])
state = sBoxLayer(state)
# Post-whitening & final permutation
state = addRoundKey(state, self.whitening_key)
state = pLayer(state)
return number2string_N(state,8)
def decrypt(self,block):
"""Decrypt 1 block (8 bytes)
Input: ciphertext block as raw string
Output: plaintex block as raw string"""
state = string2number(block)
# Final permutation & post-whitening
state = pLayer_dec(state)
state = addRoundKey(state, self.whitening_key)
# Last round R'
state = sBoxLayer_dec(state)
state = addRoundKey(state, self.roundkeys[20])
# 19 rounds R
for i in xrange(19,0,-1):
state = lLayer_dec(state)
state = sBoxLayer_dec(state)
state = addRoundKey(state, self.roundkeys[i])
# Pre-whitening & initial permutation
state = addRoundKey(state, self.whitening_key)
state = pLayer(state)
return number2string_N(state,8)
# 4 to 4-bit S-Box and its inverse
Sbox= [0x0,0x4,0x8,0xf,0x1,0x5,0xe,0x9,0x2,0x7,0xa,0xc,0xb,0xd,0x6,0x3]
Sbox_inv = [Sbox.index(x) for x in xrange(16)]
# 64-bit permutation P and its inverse
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 xrange(64)]
# Matrices for permutation in the L layer
L0_inv = L0 = [0b0000100010001000, 0b0000010001000100, 0b0000001000100010, 0b0000000100010001, 0b1000000010001000, 0b0100000001000100, 0b0010000000100010, 0b0001000000010001, 0b1000100000001000, 0b0100010000000100, 0b0010001000000010, 0b0001000100000001, 0b1000100010000000, 0b0100010001000000, 0b0010001000100000, 0b0001000100010000]
L1 = [0b1100000000010000, 0b0110000000001000, 0b0011000000000100, 0b0001100000000010, 0b0000110000000001, 0b0000011010000000, 0b0000001101000000, 0b1000000100100000, 0b1000000000011000, 0b0100000000001100, 0b0010000000000110, 0b0001000000000011, 0b0000100010000001, 0b0000010011000000, 0b0000001001100000, 0b0000000100110000]
L1_inv = [0b0000001100000010, 0b1000000100000001, 0b1100000010000000, 0b0110000001000000, 0b0011000000100000, 0b0001100000010000, 0b0000110000001000, 0b0000011000000100, 0b0001000000011000, 0b0000100000001100, 0b0000010000000110, 0b0000001000000011, 0b0000000110000001, 0b1000000011000000, 0b0100000001100000, 0b0010000000110000]
L2 = [0b0000110000000001, 0b0000011010000000, 0b0000001101000000, 0b1000000100100000, 0b1100000000010000, 0b0110000000001000, 0b0011000000000100, 0b0001100000000010, 0b0000100010000001, 0b0000010011000000, 0b0000001001100000, 0b0000000100110000, 0b1000000000011000, 0b0100000000001100, 0b0010000000000110, 0b0001000000000011]
L2_inv = [0b0011000000100000, 0b0001100000010000, 0b0000110000001000, 0b0000011000000100, 0b0000001100000010, 0b1000000100000001, 0b1100000010000000, 0b0110000001000000, 0b0000000110000001, 0b1000000011000000, 0b0100000001100000, 0b0010000000110000, 0b0001000000011000, 0b0000100000001100, 0b0000010000000110, 0b0000001000000011]
L3_inv = L3 = [0b1000100000001000, 0b0100010000000100, 0b0010001000000010, 0b0001000100000001, 0b1000100010000000, 0b0100010001000000, 0b0010001000100000, 0b0001000100010000, 0b0000100010001000, 0b0000010001000100, 0b0000001000100010, 0b0000000100010001, 0b1000000010001000, 0b0100000001000100, 0b0010000000100010, 0b0001000000010001]
def matrixMultiply(matrix, input):
"""Multiply a vector with a binary matrix
Input: matrix as [Int], where the rows are integers;
input as Int
Output: Int"""
mult = [bin(r & input).count("1") % 2 for r in matrix]
return sum([(1 << (15 - i)) * v for i,v in enumerate(mult)])
def roundKey(key, i):
"""Calculate a round key
Input: the base key (second half of it) as a raw string;
the round number
Output: the round key as raw string"""
return pLayer_dec(string2number(
key[0]
+ chr((ord(key[1]) + 193 * i) % 256)
+ key[2]
+ chr((ord(key[3]) + 165 * i) % 256)
+ key[4]
+ chr((ord(key[5]) + 81 * i) % 256)
+ key[6]
+ chr((ord(key[7]) + 197 * i) % 256)
))
def addRoundKey(state,roundkey):
return state ^ roundkey
def sBoxLayer(state):
"""SBox function for encryption
Input: 64-bit integer
Output: 64-bit integer"""
return sum([Sbox[( state >> (i * 4)) & 0xf] << (i * 4) for i in xrange(16)])
def sBoxLayer_dec(state):
"""Inverse SBox function for decryption
Input: 64-bit integer
Output: 64-bit integer"""
return sum([Sbox_inv[( state >> (i * 4)) & 0xf] << (i * 4) for i in xrange(16)])
def pLayer(state):
"""Permutation layer for encryption
Input: 64-bit integer
Output: 64-bit integer"""
return sum ([((state >> i) & 1) << PBox[i] for i in xrange(64)])
def pLayer_dec(state):
"""Permutation layer for decryption
Input: 64-bit integer
Output: 64-bit integer"""
return sum ([((state >> i) & 1) << PBox_inv[i] for i in xrange(64)])
def lLayer(state):
"""Perform the L layer:
* P (permutation)
* L0 .. L3 on all four 16-bit substrings
* P_inv (permutation inverse)
Input: the current state, as raw string
Output: the new state, as an raw string"""
state = pLayer(state)
state = (matrixMultiply(L0, (state >> 48) & 0xffff) << 48) + (
matrixMultiply(L1, (state >> 32) & 0xffff) << 32) + (
matrixMultiply(L2, (state >> 16) & 0xffff) << 16) + (
matrixMultiply(L3, state & 0xffff))
return pLayer_dec(state)
def lLayer_dec(state):
"""L layer for decryption:
* P (permutation)
* L0_inv .. L3_inv multiplication on the four 16-bit substrings, respectively
* P_inv (permutation inverse)
Input: the current state, as raw string
Output: the new state, as raw string"""
state = pLayer(state)
state = (matrixMultiply(L0_inv, (state >> 48) & 0xffff) << 48) + (
matrixMultiply(L1_inv, (state >> 32) & 0xffff) << 32) + (
matrixMultiply(L2_inv, (state >> 16) & 0xffff) << 16) + (
matrixMultiply(L3_inv, state & 0xffff))
return pLayer_dec(state)
def string2number(i):
""" Convert a string to a number
Input: string (big-endian)
Output: long or integer
"""
return int(i.encode('hex'), 16)
def number2string_N(i, N):
"""Convert a number to a string of fixed size
i: long or integer
N: length of string
Output: string (big-endian)
"""
s = '%0*x' % (N*2, i)
return s.decode('hex')
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