src/CryptoPlus/Cipher/rijndael.py

   1 """
   2 A pure python (slow) implementation of rijndael with a decent interface
   3
   4 To include -
   5
   6 from rijndael import rijndael
   7
   8 To do a key setup -
   9
  10 r = rijndael(key, block_size = 16)
  11
  12 key must be a string of length 16, 24, or 32
  13 blocksize must be 16, 24, or 32. Default is 16
  14
  15 To use -
  16
  17 ciphertext = r.encrypt(plaintext)
  18 plaintext = r.decrypt(ciphertext)
  19
  20 If any strings are of the wrong length a ValueError is thrown
  21 """
  22
  23 # ported from the Java reference code by Bram Cohen, bram@gawth.com, April 2001
  24 # this code is public domain, unless someone makes
  25 # an intellectual property claim against the reference
  26 # code, in which case it can be made public domain by
  27 # deleting all the comments and renaming all the variables
  28
  29 import copy
  30 import string
  31
  32
  33
  34 #-----------------------
  35 #TREV - ADDED BECAUSE THERE'S WARNINGS ABOUT INT OVERFLOW BEHAVIOR CHANGING IN
  36 #2.4.....
  37 import os
  38 if os.name != "java":
  39     import exceptions
  40     if hasattr(exceptions, "FutureWarning"):
  41         import warnings
  42         warnings.filterwarnings("ignore", category=FutureWarning, append=1)
  43 #-----------------------
  44
  45
  46
  47 shifts = [[[0, 0], [1, 3], [2, 2], [3, 1]],
  48           [[0, 0], [1, 5], [2, 4], [3, 3]],
  49           [[0, 0], [1, 7], [3, 5], [4, 4]]]
  50
  51 # [keysize][block_size]
  52 num_rounds = {16: {16: 10, 24: 12, 32: 14}, 24: {16: 12, 24: 12, 32: 14}, 32: {16: 14, 24: 14, 32: 14}}
  53
  54 A = [[1, 1, 1, 1, 1, 0, 0, 0],
  55      [0, 1, 1, 1, 1, 1, 0, 0],
  56      [0, 0, 1, 1, 1, 1, 1, 0],
  57      [0, 0, 0, 1, 1, 1, 1, 1],
  58      [1, 0, 0, 0, 1, 1, 1, 1],
  59      [1, 1, 0, 0, 0, 1, 1, 1],
  60      [1, 1, 1, 0, 0, 0, 1, 1],
  61      [1, 1, 1, 1, 0, 0, 0, 1]]
  62
  63 # produce log and alog tables, needed for multiplying in the
  64 # field GF(2^m) (generator = 3)
  65 alog = [1]
  66 for i in xrange(255):
  67     j = (alog[-1] << 1) ^ alog[-1]
  68     if j & 0x100 != 0:
  69         j ^= 0x11B
  70     alog.append(j)
  71
  72 log = [0] * 256
  73 for i in xrange(1, 255):
  74     log[alog[i]] = i
  75
  76 # multiply two elements of GF(2^m)
  77 def mul(a, b):
  78     if a == 0 or b == 0:
  79         return 0
  80     return alog[(log[a & 0xFF] + log[b & 0xFF]) % 255]
  81
  82 # substitution box based on F^{-1}(x)
  83 box = [[0] * 8 for i in xrange(256)]
  84 box[1][7] = 1
  85 for i in xrange(2, 256):
  86     j = alog[255 - log[i]]
  87     for t in xrange(8):
  88         box[i][t] = (j >> (7 - t)) & 0x01
  89
  90 B = [0, 1, 1, 0, 0, 0, 1, 1]
  91
  92 # affine transform:  box[i] <- B + A*box[i]
  93 cox = [[0] * 8 for i in xrange(256)]
  94 for i in xrange(256):
  95     for t in xrange(8):
  96         cox[i][t] = B[t]
  97         for j in xrange(8):
  98             cox[i][t] ^= A[t][j] * box[i][j]
  99
 100 # S-boxes and inverse S-boxes
 101 S =  [0] * 256
 102 Si = [0] * 256
 103 for i in xrange(256):
 104     S[i] = cox[i][0] << 7
 105     for t in xrange(1, 8):
 106         S[i] ^= cox[i][t] << (7-t)
 107     Si[S[i] & 0xFF] = i
 108
 109 # T-boxes
 110 G = [[2, 1, 1, 3],
 111     [3, 2, 1, 1],
 112     [1, 3, 2, 1],
 113     [1, 1, 3, 2]]
 114
 115 AA = [[0] * 8 for i in xrange(4)]
 116
 117 for i in xrange(4):
 118     for j in xrange(4):
 119         AA[i][j] = G[i][j]
 120         AA[i][i+4] = 1
 121
 122 for i in xrange(4):
 123     pivot = AA[i][i]
 124     if pivot == 0:
 125         t = i + 1
 126         while AA[t][i] == 0 and t < 4:
 127             t += 1
 128             assert t != 4, 'G matrix must be invertible'
 129             for j in xrange(8):
 130                 AA[i][j], AA[t][j] = AA[t][j], AA[i][j]
 131             pivot = AA[i][i]
 132     for j in xrange(8):
 133         if AA[i][j] != 0:
 134             AA[i][j] = alog[(255 + log[AA[i][j] & 0xFF] - log[pivot & 0xFF]) % 255]
 135     for t in xrange(4):
 136         if i != t:
 137             for j in xrange(i+1, 8):
 138                 AA[t][j] ^= mul(AA[i][j], AA[t][i])
 139             AA[t][i] = 0
 140
 141 iG = [[0] * 4 for i in xrange(4)]
 142
 143 for i in xrange(4):
 144     for j in xrange(4):
 145         iG[i][j] = AA[i][j + 4]
 146
 147 def mul4(a, bs):
 148     if a == 0:
 149         return 0
 150     r = 0
 151     for b in bs:
 152         r <<= 8
 153         if b != 0:
 154             r = r | mul(a, b)
 155     return r
 156
 157 T1 = []
 158 T2 = []
 159 T3 = []
 160 T4 = []
 161 T5 = []
 162 T6 = []
 163 T7 = []
 164 T8 = []
 165 U1 = []
 166 U2 = []
 167 U3 = []
 168 U4 = []
 169
 170 for t in xrange(256):
 171     s = S[t]
 172     T1.append(mul4(s, G[0]))
 173     T2.append(mul4(s, G[1]))
 174     T3.append(mul4(s, G[2]))
 175     T4.append(mul4(s, G[3]))
 176
 177     s = Si[t]
 178     T5.append(mul4(s, iG[0]))
 179     T6.append(mul4(s, iG[1]))
 180     T7.append(mul4(s, iG[2]))
 181     T8.append(mul4(s, iG[3]))
 182
 183     U1.append(mul4(t, iG[0]))
 184     U2.append(mul4(t, iG[1]))
 185     U3.append(mul4(t, iG[2]))
 186     U4.append(mul4(t, iG[3]))
 187
 188 # round constants
 189 rcon = [1]
 190 r = 1
 191 for t in xrange(1, 30):
 192     r = mul(2, r)
 193     rcon.append(r)
 194
 195 del A
 196 del AA
 197 del pivot
 198 del B
 199 del G
 200 del box
 201 del log
 202 del alog
 203 del i
 204 del j
 205 del r
 206 del s
 207 del t
 208 del mul
 209 del mul4
 210 del cox
 211 del iG
 212
 213 class rijndael:
 214     def __init__(self, key, block_size = 16):
 215         if block_size != 16 and block_size != 24 and block_size != 32:
 216             raise ValueError('Invalid block size: ' + str(block_size))
 217         if len(key) != 16 and len(key) != 24 and len(key) != 32:
 218             raise ValueError('Invalid key size: ' + str(len(key)))
 219         self.block_size = block_size
 220
 221         ROUNDS = num_rounds[len(key)][block_size]
 222         BC = block_size / 4
 223         # encryption round keys
 224         Ke = [[0] * BC for i in xrange(ROUNDS + 1)]
 225         # decryption round keys
 226         Kd = [[0] * BC for i in xrange(ROUNDS + 1)]
 227         ROUND_KEY_COUNT = (ROUNDS + 1) * BC
 228         KC = len(key) / 4
 229
 230         # copy user material bytes into temporary ints
 231         tk = []
 232         for i in xrange(0, KC):
 233             tk.append((ord(key[i * 4]) << 24) | (ord(key[i * 4 + 1]) << 16) |
 234                 (ord(key[i * 4 + 2]) << 8) | ord(key[i * 4 + 3]))
 235
 236         # copy values into round key arrays
 237         t = 0
 238         j = 0
 239         while j < KC and t < ROUND_KEY_COUNT:
 240             Ke[t / BC][t % BC] = tk[j]
 241             Kd[ROUNDS - (t / BC)][t % BC] = tk[j]
 242             j += 1
 243             t += 1
 244         tt = 0
 245         rconpointer = 0
 246         while t < ROUND_KEY_COUNT:
 247             # extrapolate using phi (the round key evolution function)
 248             tt = tk[KC - 1]
 249             tk[0] ^= (S[(tt >> 16) & 0xFF] & 0xFF) << 24 ^  \
 250                      (S[(tt >>  8) & 0xFF] & 0xFF) << 16 ^  \
 251                      (S[ tt        & 0xFF] & 0xFF) <<  8 ^  \
 252                      (S[(tt >> 24) & 0xFF] & 0xFF)       ^  \
 253                      (rcon[rconpointer]    & 0xFF) << 24
 254             rconpointer += 1
 255             if KC != 8:
 256                 for i in xrange(1, KC):
 257                     tk[i] ^= tk[i-1]
 258             else:
 259                 for i in xrange(1, KC / 2):
 260                     tk[i] ^= tk[i-1]
 261                 tt = tk[KC / 2 - 1]
 262                 tk[KC / 2] ^= (S[ tt        & 0xFF] & 0xFF)       ^ \
 263                               (S[(tt >>  8) & 0xFF] & 0xFF) <<  8 ^ \
 264                               (S[(tt >> 16) & 0xFF] & 0xFF) << 16 ^ \
 265                               (S[(tt >> 24) & 0xFF] & 0xFF) << 24
 266                 for i in xrange(KC / 2 + 1, KC):
 267                     tk[i] ^= tk[i-1]
 268             # copy values into round key arrays
 269             j = 0
 270             while j < KC and t < ROUND_KEY_COUNT:
 271                 Ke[t / BC][t % BC] = tk[j]
 272                 Kd[ROUNDS - (t / BC)][t % BC] = tk[j]
 273                 j += 1
 274                 t += 1
 275         # inverse MixColumn where needed
 276         for r in xrange(1, ROUNDS):
 277             for j in xrange(BC):
 278                 tt = Kd[r][j]
 279                 Kd[r][j] = U1[(tt >> 24) & 0xFF] ^ \
 280                            U2[(tt >> 16) & 0xFF] ^ \
 281                            U3[(tt >>  8) & 0xFF] ^ \
 282                            U4[ tt        & 0xFF]
 283         self.Ke = Ke
 284         self.Kd = Kd
 285
 286     def encrypt(self, plaintext):
 287         if len(plaintext) != self.block_size:
 288             raise ValueError('wrong block length, expected ' + str(self.block_size) + ' got ' + str(len(plaintext)))
 289         Ke = self.Ke
 290
 291         BC = self.block_size / 4
 292         ROUNDS = len(Ke) - 1
 293         if BC == 4:
 294             SC = 0
 295         elif BC == 6:
 296             SC = 1
 297         else:
 298             SC = 2
 299         s1 = shifts[SC][1][0]
 300         s2 = shifts[SC][2][0]
 301         s3 = shifts[SC][3][0]
 302         a = [0] * BC
 303         # temporary work array
 304         t = []
 305         # plaintext to ints + key
 306         for i in xrange(BC):
 307             t.append((ord(plaintext[i * 4    ]) << 24 |
 308                       ord(plaintext[i * 4 + 1]) << 16 |
 309                       ord(plaintext[i * 4 + 2]) <<  8 |
 310                       ord(plaintext[i * 4 + 3])        ) ^ Ke[0][i])
 311         # apply round transforms
 312         for r in xrange(1, ROUNDS):
 313             for i in xrange(BC):
 314                 a[i] = (T1[(t[ i           ] >> 24) & 0xFF] ^
 315                         T2[(t[(i + s1) % BC] >> 16) & 0xFF] ^
 316                         T3[(t[(i + s2) % BC] >>  8) & 0xFF] ^
 317                         T4[ t[(i + s3) % BC]        & 0xFF]  ) ^ Ke[r][i]
 318             t = copy.copy(a)
 319         # last round is special
 320         result = []
 321         for i in xrange(BC):
 322             tt = Ke[ROUNDS][i]
 323             result.append((S[(t[ i           ] >> 24) & 0xFF] ^ (tt >> 24)) & 0xFF)
 324             result.append((S[(t[(i + s1) % BC] >> 16) & 0xFF] ^ (tt >> 16)) & 0xFF)
 325             result.append((S[(t[(i + s2) % BC] >>  8) & 0xFF] ^ (tt >>  8)) & 0xFF)
 326             result.append((S[ t[(i + s3) % BC]        & 0xFF] ^  tt       ) & 0xFF)
 327         return string.join(map(chr, result), '')
 328
 329     def decrypt(self, ciphertext):
 330         if len(ciphertext) != self.block_size:
 331             raise ValueError('wrong block length, expected ' + str(self.block_size) + ' got ' + str(len(plaintext)))
 332         Kd = self.Kd
 333
 334         BC = self.block_size / 4
 335         ROUNDS = len(Kd) - 1
 336         if BC == 4:
 337             SC = 0
 338         elif BC == 6:
 339             SC = 1
 340         else:
 341             SC = 2
 342         s1 = shifts[SC][1][1]
 343         s2 = shifts[SC][2][1]
 344         s3 = shifts[SC][3][1]
 345         a = [0] * BC
 346         # temporary work array
 347         t = [0] * BC
 348         # ciphertext to ints + key
 349         for i in xrange(BC):
 350             t[i] = (ord(ciphertext[i * 4    ]) << 24 |
 351                     ord(ciphertext[i * 4 + 1]) << 16 |
 352                     ord(ciphertext[i * 4 + 2]) <<  8 |
 353                     ord(ciphertext[i * 4 + 3])        ) ^ Kd[0][i]
 354         # apply round transforms
 355         for r in xrange(1, ROUNDS):
 356             for i in xrange(BC):
 357                 a[i] = (T5[(t[ i           ] >> 24) & 0xFF] ^
 358                         T6[(t[(i + s1) % BC] >> 16) & 0xFF] ^
 359                         T7[(t[(i + s2) % BC] >>  8) & 0xFF] ^
 360                         T8[ t[(i + s3) % BC]        & 0xFF]  ) ^ Kd[r][i]
 361             t = copy.copy(a)
 362         # last round is special
 363         result = []
 364         for i in xrange(BC):
 365             tt = Kd[ROUNDS][i]
 366             result.append((Si[(t[ i           ] >> 24) & 0xFF] ^ (tt >> 24)) & 0xFF)
 367             result.append((Si[(t[(i + s1) % BC] >> 16) & 0xFF] ^ (tt >> 16)) & 0xFF)
 368             result.append((Si[(t[(i + s2) % BC] >>  8) & 0xFF] ^ (tt >>  8)) & 0xFF)
 369             result.append((Si[ t[(i + s3) % BC]        & 0xFF] ^  tt       ) & 0xFF)
 370         return string.join(map(chr, result), '')
 371
 372 def encrypt(key, block):
 373     return rijndael(key, len(block)).encrypt(block)
 374
 375 def decrypt(key, block):
 376     return rijndael(key, len(block)).decrypt(block)
 377
 378 def test():
 379     def t(kl, bl):
 380         b = 'b' * bl
 381         r = rijndael('a' * kl, bl)
 382         assert r.decrypt(r.encrypt(b)) == b
 383     t(16, 16)
 384     t(16, 24)
 385     t(16, 32)
 386     t(24, 16)
 387     t(24, 24)
 388     t(24, 32)
 389     t(32, 16)
 390     t(32, 24)
 391     t(32, 32)
 392