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- #!/usr/bin/python
- #
- # aes.py: implements AES - Advanced Encryption Standard
- # from the SlowAES project, http://code.google.com/p/slowaes/
- #
- # Copyright (c) 2008 Josh Davis ( http://www.josh-davis.org ),
- # Alex Martelli ( http://www.aleax.it )
- #
- # Ported from C code written by Laurent Haan ( http://www.progressive-coding.com )
- #
- # Licensed under the Apache License, Version 2.0
- # http://www.apache.org/licenses/
- #
- # modified by Ella Rose to demonstrate the weakness of linear ciphers
- import os
- import sys
- import math
- class AES(object):
- '''AES funtions for a single block
- '''
- # Very annoying code: all is for an object, but no state is kept!
- # Should just be plain functions in a AES modlule.
- # valid key sizes
- keySize = dict(SIZE_128=16, SIZE_192=24, SIZE_256=32)
- # Rijndael S-box
- #sbox = [0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67,
- # 0x2b, 0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59,
- # 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7,
- # 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1,
- # 0x71, 0xd8, 0x31, 0x15, 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05,
- # 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83,
- # 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29,
- # 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b,
- # 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa,
- # 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c,
- # 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc,
- # 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec,
- # 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19,
- # 0x73, 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee,
- # 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49,
- # 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
- # 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4,
- # 0xea, 0x65, 0x7a, 0xae, 0x08, 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6,
- # 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, 0x70,
- # 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9,
- # 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e,
- # 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1,
- # 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0,
- # 0x54, 0xbb, 0x16]
- sbox = range(256)
- # Rijndael Inverted S-box
- #rsbox = [0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3,
- # 0x9e, 0x81, 0xf3, 0xd7, 0xfb , 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f,
- # 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb , 0x54,
- # 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b,
- # 0x42, 0xfa, 0xc3, 0x4e , 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24,
- # 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25 , 0x72, 0xf8,
- # 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d,
- # 0x65, 0xb6, 0x92 , 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda,
- # 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84 , 0x90, 0xd8, 0xab,
- # 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3,
- # 0x45, 0x06 , 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1,
- # 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b , 0x3a, 0x91, 0x11, 0x41,
- # 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6,
- # 0x73 , 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9,
- # 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e , 0x47, 0xf1, 0x1a, 0x71, 0x1d,
- # 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b ,
- # 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0,
- # 0xfe, 0x78, 0xcd, 0x5a, 0xf4 , 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07,
- # 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f , 0x60,
- # 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f,
- # 0x93, 0xc9, 0x9c, 0xef , 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5,
- # 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61 , 0x17, 0x2b,
- # 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55,
- # 0x21, 0x0c, 0x7d]
- rsbox = range(256)
- def getSBoxValue(self,num):
- """Retrieves a given S-Box Value"""
- return self.sbox[num]
- def getSBoxInvert(self,num):
- """Retrieves a given Inverted S-Box Value"""
- return self.rsbox[num]
- def rotate(self, word):
- """ Rijndael's key schedule rotate operation.
- Rotate a word eight bits to the left: eg, rotate(1d2c3a4f) == 2c3a4f1d
- Word is an char list of size 4 (32 bits overall).
- """
- return word[1:] + word[:1]
- # Rijndael Rcon
- Rcon = [0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36,
- 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97,
- 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72,
- 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66,
- 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04,
- 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d,
- 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3,
- 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61,
- 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a,
- 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40,
- 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc,
- 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5,
- 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a,
- 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d,
- 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c,
- 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35,
- 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4,
- 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc,
- 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08,
- 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
- 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d,
- 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2,
- 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74,
- 0xe8, 0xcb ]
- def getRconValue(self, num):
- """Retrieves a given Rcon Value"""
- return self.Rcon[num]
- def core(self, word, iteration):
- """Key schedule core."""
- # rotate the 32-bit word 8 bits to the left
- word = self.rotate(word)
- # apply S-Box substitution on all 4 parts of the 32-bit word
- for i in range(4):
- word[i] = self.getSBoxValue(word[i])
- # XOR the output of the rcon operation with i to the first part
- # (leftmost) only
- word[0] = word[0] ^ self.getRconValue(iteration)
- return word
- def expandKey(self, key, size, expandedKeySize):
- """Rijndael's key expansion.
- Expands an 128,192,256 key into an 176,208,240 bytes key
- expandedKey is a char list of large enough size,
- key is the non-expanded key.
- """
- # current expanded keySize, in bytes
- currentSize = 0
- rconIteration = 1
- expandedKey = [0] * expandedKeySize
- # set the 16, 24, 32 bytes of the expanded key to the input key
- for j in range(size):
- expandedKey[j] = key[j]
- currentSize += size
- while currentSize < expandedKeySize:
- # assign the previous 4 bytes to the temporary value t
- t = expandedKey[currentSize-4:currentSize]
- # every 16,24,32 bytes we apply the core schedule to t
- # and increment rconIteration afterwards
- if currentSize % size == 0:
- t = self.core(t, rconIteration)
- rconIteration += 1
- # For 256-bit keys, we add an extra sbox to the calculation
- if size == self.keySize["SIZE_256"] and ((currentSize % size) == 16):
- for l in range(4): t[l] = self.getSBoxValue(t[l])
- # We XOR t with the four-byte block 16,24,32 bytes before the new
- # expanded key. This becomes the next four bytes in the expanded
- # key.
- for m in range(4):
- expandedKey[currentSize] = expandedKey[currentSize - size] ^ \
- t[m]
- currentSize += 1
- return expandedKey
- def addRoundKey(self, state, roundKey):
- """Adds (XORs) the round key to the state."""
- for i in range(16):
- state[i] ^= roundKey[i]
- return state
- def createRoundKey(self, expandedKey, roundKeyPointer):
- """Create a round key.
- Creates a round key from the given expanded key and the
- position within the expanded key.
- """
- roundKey = [0] * 16
- for i in range(4):
- for j in range(4):
- roundKey[j*4+i] = expandedKey[roundKeyPointer + i*4 + j]
- return roundKey
- def galois_multiplication(self, a, b):
- """Galois multiplication of 8 bit characters a and b."""
- p = 0
- for counter in range(8):
- if b & 1: p ^= a
- hi_bit_set = a & 0x80
- a <<= 1
- # keep a 8 bit
- a &= 0xFF
- if hi_bit_set:
- a ^= 0x1b
- b >>= 1
- return p
- #
- # substitute all the values from the state with the value in the SBox
- # using the state value as index for the SBox
- #
- def subBytes(self, state, isInv):
- if isInv: getter = self.getSBoxInvert
- else: getter = self.getSBoxValue
- for i in range(16): state[i] = getter(state[i])
- return state
- # iterate over the 4 rows and call shiftRow() with that row
- def shiftRows(self, state, isInv):
- for i in range(4):
- state = self.shiftRow(state, i*4, i, isInv)
- return state
- # each iteration shifts the row to the left by 1
- def shiftRow(self, state, statePointer, nbr, isInv):
- for i in range(nbr):
- if isInv:
- state[statePointer:statePointer+4] = \
- state[statePointer+3:statePointer+4] + \
- state[statePointer:statePointer+3]
- else:
- state[statePointer:statePointer+4] = \
- state[statePointer+1:statePointer+4] + \
- state[statePointer:statePointer+1]
- return state
- # galois multiplication of the 4x4 matrix
- def mixColumns(self, state, isInv):
- # iterate over the 4 columns
- for i in range(4):
- # construct one column by slicing over the 4 rows
- column = state[i:i+16:4]
- # apply the mixColumn on one column
- column = self.mixColumn(column, isInv)
- # put the values back into the state
- state[i:i+16:4] = column
- return state
- # galois multiplication of 1 column of the 4x4 matrix
- def mixColumn(self, column, isInv):
- if isInv: mult = [14, 9, 13, 11]
- else: mult = [2, 1, 1, 3]
- cpy = list(column)
- g = self.galois_multiplication
- column[0] = g(cpy[0], mult[0]) ^ g(cpy[3], mult[1]) ^ \
- g(cpy[2], mult[2]) ^ g(cpy[1], mult[3])
- column[1] = g(cpy[1], mult[0]) ^ g(cpy[0], mult[1]) ^ \
- g(cpy[3], mult[2]) ^ g(cpy[2], mult[3])
- column[2] = g(cpy[2], mult[0]) ^ g(cpy[1], mult[1]) ^ \
- g(cpy[0], mult[2]) ^ g(cpy[3], mult[3])
- column[3] = g(cpy[3], mult[0]) ^ g(cpy[2], mult[1]) ^ \
- g(cpy[1], mult[2]) ^ g(cpy[0], mult[3])
- return column
- # applies the 4 operations of the forward round in sequence
- def aes_round(self, state, roundKey):
- state = self.subBytes(state, False)
- state = self.shiftRows(state, False)
- state = self.mixColumns(state, False)
- state = self.addRoundKey(state, roundKey)
- return state
- def aes_round_no_key(self, state):
- state = self.subBytes(state, False)
- state = self.shiftRows(state, False)
- state = self.mixColumns(state, False)
- return state
- # applies the 4 operations of the inverse round in sequence
- def aes_invRound(self, state, roundKey):
- state = self.shiftRows(state, True)
- state = self.subBytes(state, True)
- state = self.addRoundKey(state, roundKey)
- state = self.mixColumns(state, True)
- return state
- # Perform the initial operations, the standard round, and the final
- # operations of the forward aes, creating a round key for each round
- def aes_main(self, state, expandedKey, nbrRounds):
- state = self.addRoundKey(state, self.createRoundKey(expandedKey, 0))
- i = 1
- while i < nbrRounds:
- state = self.aes_round(state,
- self.createRoundKey(expandedKey, 16*i))
- i += 1
- state = self.subBytes(state, False)
- state = self.shiftRows(state, False)
- state = self.addRoundKey(state,
- self.createRoundKey(expandedKey, 16*nbrRounds))
- return state
- # Perform the initial operations, the standard round, and the final
- # operations of the inverse aes, creating a round key for each round
- def aes_invMain(self, state, expandedKey, nbrRounds):
- state = self.addRoundKey(state,
- self.createRoundKey(expandedKey, 16*nbrRounds))
- i = nbrRounds - 1
- while i > 0:
- state = self.aes_invRound(state,
- self.createRoundKey(expandedKey, 16*i))
- i -= 1
- state = self.shiftRows(state, True)
- state = self.subBytes(state, True)
- state = self.addRoundKey(state, self.createRoundKey(expandedKey, 0))
- return state
- # encrypts a 128 bit input block against the given key of size specified
- def encrypt(self, iput, key, size):
- output = [0] * 16
- # the number of rounds
- nbrRounds = 0
- # the 128 bit block to encode
- block = [0] * 16
- # set the number of rounds
- if size == self.keySize["SIZE_128"]: nbrRounds = 10
- elif size == self.keySize["SIZE_192"]: nbrRounds = 12
- elif size == self.keySize["SIZE_256"]: nbrRounds = 14
- else: return None
- # the expanded keySize
- expandedKeySize = 16*(nbrRounds+1)
- # Set the block values, for the block:
- # a0,0 a0,1 a0,2 a0,3
- # a1,0 a1,1 a1,2 a1,3
- # a2,0 a2,1 a2,2 a2,3
- # a3,0 a3,1 a3,2 a3,3
- # the mapping order is a0,0 a1,0 a2,0 a3,0 a0,1 a1,1 ... a2,3 a3,3
- #
- # iterate over the columns
- for i in range(4):
- # iterate over the rows
- for j in range(4):
- block[(i+(j*4))] = iput[(i*4)+j]
- # expand the key into an 176, 208, 240 bytes key
- # the expanded key
- expandedKey = self.expandKey(key, size, expandedKeySize)
- # encrypt the block using the expandedKey
- block = self.aes_main(block, expandedKey, nbrRounds)
- # unmap the block again into the output
- for k in range(4):
- # iterate over the rows
- for l in range(4):
- output[(k*4)+l] = block[(k+(l*4))]
- return output
- # decrypts a 128 bit input block against the given key of size specified
- def decrypt(self, iput, key, size):
- output = [0] * 16
- # the number of rounds
- nbrRounds = 0
- # the 128 bit block to decode
- block = [0] * 16
- # set the number of rounds
- if size == self.keySize["SIZE_128"]: nbrRounds = 10
- elif size == self.keySize["SIZE_192"]: nbrRounds = 12
- elif size == self.keySize["SIZE_256"]: nbrRounds = 14
- else: return None
- # the expanded keySize
- expandedKeySize = 16*(nbrRounds+1)
- # Set the block values, for the block:
- # a0,0 a0,1 a0,2 a0,3
- # a1,0 a1,1 a1,2 a1,3
- # a2,0 a2,1 a2,2 a2,3
- # a3,0 a3,1 a3,2 a3,3
- # the mapping order is a0,0 a1,0 a2,0 a3,0 a0,1 a1,1 ... a2,3 a3,3
- # iterate over the columns
- for i in range(4):
- # iterate over the rows
- for j in range(4):
- block[(i+(j*4))] = iput[(i*4)+j]
- # expand the key into an 176, 208, 240 bytes key
- expandedKey = self.expandKey(key, size, expandedKeySize)
- # decrypt the block using the expandedKey
- block = self.aes_invMain(block, expandedKey, nbrRounds)
- # unmap the block again into the output
- for k in range(4):
- # iterate over the rows
- for l in range(4):
- output[(k*4)+l] = block[(k+(l*4))]
- return output
- def test_break():
- size = 16
- key = range(size)
- attack_plaintext = [0] * size
- encryptor = AES()
- equivalent_key = encryptor.encrypt(attack_plaintext[:], key, size)
- _check1 = encryptor.decrypt(equivalent_key[:], key, size)
- assert _check1 == attack_plaintext
- from os import urandom
- random_plaintext = list(bytearray(urandom(size)))
- ciphertext = encryptor.encrypt(random_plaintext[:], key, size)
- partial_plaintext = [equivalent_key[i] ^ ciphertext[i] for i in range(16)]
- encryptor.addRoundKey = lambda state, __: state
- recovered_plaintext = encryptor.decrypt(partial_plaintext, key, size) # key not actually used now
- assert recovered_plaintext == random_plaintext, (recovered_plaintext, random_plaintext)
- if __name__ == "__main__":
- test_break()
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