""" A pure python (slow) implementation of rijndael with a decent interface To include - from rijndael import rijndael To do a key setup - r = rijndael(key, block_size = 16) key must be a string of length 16, 24, or 32 blocksize must be 16, 24, or 32. Default is 16 To use - ciphertext = r.encrypt(plaintext) plaintext = r.decrypt(ciphertext) If any strings are of the wrong length a ValueError is thrown """ # ported from the Java reference code by Bram Cohen, bram@gawth.com, April 2001 # this code is public domain, unless someone makes # an intellectual property claim against the reference # code, in which case it can be made public domain by # deleting all the comments and renaming all the variables import copy import string #----------------------- #TREV - ADDED BECAUSE THERE'S WARNINGS ABOUT INT OVERFLOW BEHAVIOR CHANGING IN #2.4..... import os if os.name != "java": import exceptions if hasattr(exceptions, "FutureWarning"): import warnings warnings.filterwarnings("ignore", category=FutureWarning, append=1) #----------------------- shifts = [[[0, 0], [1, 3], [2, 2], [3, 1]], [[0, 0], [1, 5], [2, 4], [3, 3]], [[0, 0], [1, 7], [3, 5], [4, 4]]] # [keysize][block_size] num_rounds = {16: {16: 10, 24: 12, 32: 14}, 24: {16: 12, 24: 12, 32: 14}, 32: {16: 14, 24: 14, 32: 14}} A = [[1, 1, 1, 1, 1, 0, 0, 0], [0, 1, 1, 1, 1, 1, 0, 0], [0, 0, 1, 1, 1, 1, 1, 0], [0, 0, 0, 1, 1, 1, 1, 1], [1, 0, 0, 0, 1, 1, 1, 1], [1, 1, 0, 0, 0, 1, 1, 1], [1, 1, 1, 0, 0, 0, 1, 1], [1, 1, 1, 1, 0, 0, 0, 1]] # produce log and alog tables, needed for multiplying in the # field GF(2^m) (generator = 3) alog = [1] for i in xrange(255): j = (alog[-1] << 1) ^ alog[-1] if j & 0x100 != 0: j ^= 0x11B alog.append(j) log = [0] * 256 for i in xrange(1, 255): log[alog[i]] = i # multiply two elements of GF(2^m) def mul(a, b): if a == 0 or b == 0: return 0 return alog[(log[a & 0xFF] + log[b & 0xFF]) % 255] # substitution box based on F^{-1}(x) box = [[0] * 8 for i in xrange(256)] box[1][7] = 1 for i in xrange(2, 256): j = alog[255 - log[i]] for t in xrange(8): box[i][t] = (j >> (7 - t)) & 0x01 B = [0, 1, 1, 0, 0, 0, 1, 1] # affine transform: box[i] <- B + A*box[i] cox = [[0] * 8 for i in xrange(256)] for i in xrange(256): for t in xrange(8): cox[i][t] = B[t] for j in xrange(8): cox[i][t] ^= A[t][j] * box[i][j] # S-boxes and inverse S-boxes S = [0] * 256 Si = [0] * 256 for i in xrange(256): S[i] = cox[i][0] << 7 for t in xrange(1, 8): S[i] ^= cox[i][t] << (7-t) Si[S[i] & 0xFF] = i # T-boxes G = [[2, 1, 1, 3], [3, 2, 1, 1], [1, 3, 2, 1], [1, 1, 3, 2]] AA = [[0] * 8 for i in xrange(4)] for i in xrange(4): for j in xrange(4): AA[i][j] = G[i][j] AA[i][i+4] = 1 for i in xrange(4): pivot = AA[i][i] if pivot == 0: t = i + 1 while AA[t][i] == 0 and t < 4: t += 1 assert t != 4, 'G matrix must be invertible' for j in xrange(8): AA[i][j], AA[t][j] = AA[t][j], AA[i][j] pivot = AA[i][i] for j in xrange(8): if AA[i][j] != 0: AA[i][j] = alog[(255 + log[AA[i][j] & 0xFF] - log[pivot & 0xFF]) % 255] for t in xrange(4): if i != t: for j in xrange(i+1, 8): AA[t][j] ^= mul(AA[i][j], AA[t][i]) AA[t][i] = 0 iG = [[0] * 4 for i in xrange(4)] for i in xrange(4): for j in xrange(4): iG[i][j] = AA[i][j + 4] def mul4(a, bs): if a == 0: return 0 r = 0 for b in bs: r <<= 8 if b != 0: r = r | mul(a, b) return r T1 = [] T2 = [] T3 = [] T4 = [] T5 = [] T6 = [] T7 = [] T8 = [] U1 = [] U2 = [] U3 = [] U4 = [] for t in xrange(256): s = S[t] T1.append(mul4(s, G[0])) T2.append(mul4(s, G[1])) T3.append(mul4(s, G[2])) T4.append(mul4(s, G[3])) s = Si[t] T5.append(mul4(s, iG[0])) T6.append(mul4(s, iG[1])) T7.append(mul4(s, iG[2])) T8.append(mul4(s, iG[3])) U1.append(mul4(t, iG[0])) U2.append(mul4(t, iG[1])) U3.append(mul4(t, iG[2])) U4.append(mul4(t, iG[3])) # round constants rcon = [1] r = 1 for t in xrange(1, 30): r = mul(2, r) rcon.append(r) del A del AA del pivot del B del G del box del log del alog del i del j del r del s del t del mul del mul4 del cox del iG class rijndael: def __init__(self, key, block_size = 16): if block_size != 16 and block_size != 24 and block_size != 32: raise ValueError('Invalid block size: ' + str(block_size)) if len(key) != 16 and len(key) != 24 and len(key) != 32: raise ValueError('Invalid key size: ' + str(len(key))) self.block_size = block_size ROUNDS = num_rounds[len(key)][block_size] BC = block_size / 4 # encryption round keys Ke = [[0] * BC for i in xrange(ROUNDS + 1)] # decryption round keys Kd = [[0] * BC for i in xrange(ROUNDS + 1)] ROUND_KEY_COUNT = (ROUNDS + 1) * BC KC = len(key) / 4 # copy user material bytes into temporary ints tk = [] for i in xrange(0, KC): tk.append((ord(key[i * 4]) << 24) | (ord(key[i * 4 + 1]) << 16) | (ord(key[i * 4 + 2]) << 8) | ord(key[i * 4 + 3])) # copy values into round key arrays t = 0 j = 0 while j < KC and t < ROUND_KEY_COUNT: Ke[t / BC][t % BC] = tk[j] Kd[ROUNDS - (t / BC)][t % BC] = tk[j] j += 1 t += 1 tt = 0 rconpointer = 0 while t < ROUND_KEY_COUNT: # extrapolate using phi (the round key evolution function) tt = tk[KC - 1] tk[0] ^= (S[(tt >> 16) & 0xFF] & 0xFF) << 24 ^ \ (S[(tt >> 8) & 0xFF] & 0xFF) << 16 ^ \ (S[ tt & 0xFF] & 0xFF) << 8 ^ \ (S[(tt >> 24) & 0xFF] & 0xFF) ^ \ (rcon[rconpointer] & 0xFF) << 24 rconpointer += 1 if KC != 8: for i in xrange(1, KC): tk[i] ^= tk[i-1] else: for i in xrange(1, KC / 2): tk[i] ^= tk[i-1] tt = tk[KC / 2 - 1] tk[KC / 2] ^= (S[ tt & 0xFF] & 0xFF) ^ \ (S[(tt >> 8) & 0xFF] & 0xFF) << 8 ^ \ (S[(tt >> 16) & 0xFF] & 0xFF) << 16 ^ \ (S[(tt >> 24) & 0xFF] & 0xFF) << 24 for i in xrange(KC / 2 + 1, KC): tk[i] ^= tk[i-1] # copy values into round key arrays j = 0 while j < KC and t < ROUND_KEY_COUNT: Ke[t / BC][t % BC] = tk[j] Kd[ROUNDS - (t / BC)][t % BC] = tk[j] j += 1 t += 1 # inverse MixColumn where needed for r in xrange(1, ROUNDS): for j in xrange(BC): tt = Kd[r][j] Kd[r][j] = U1[(tt >> 24) & 0xFF] ^ \ U2[(tt >> 16) & 0xFF] ^ \ U3[(tt >> 8) & 0xFF] ^ \ U4[ tt & 0xFF] self.Ke = Ke self.Kd = Kd def encrypt(self, plaintext): if len(plaintext) != self.block_size: raise ValueError('wrong block length, expected ' + str(self.block_size) + ' got ' + str(len(plaintext))) Ke = self.Ke BC = self.block_size / 4 ROUNDS = len(Ke) - 1 if BC == 4: SC = 0 elif BC == 6: SC = 1 else: SC = 2 s1 = shifts[SC][1][0] s2 = shifts[SC][2][0] s3 = shifts[SC][3][0] a = [0] * BC # temporary work array t = [] # plaintext to ints + key for i in xrange(BC): t.append((ord(plaintext[i * 4 ]) << 24 | ord(plaintext[i * 4 + 1]) << 16 | ord(plaintext[i * 4 + 2]) << 8 | ord(plaintext[i * 4 + 3]) ) ^ Ke[0][i]) # apply round transforms for r in xrange(1, ROUNDS): for i in xrange(BC): a[i] = (T1[(t[ i ] >> 24) & 0xFF] ^ T2[(t[(i + s1) % BC] >> 16) & 0xFF] ^ T3[(t[(i + s2) % BC] >> 8) & 0xFF] ^ T4[ t[(i + s3) % BC] & 0xFF] ) ^ Ke[r][i] t = copy.copy(a) # last round is special result = [] for i in xrange(BC): tt = Ke[ROUNDS][i] result.append((S[(t[ i ] >> 24) & 0xFF] ^ (tt >> 24)) & 0xFF) result.append((S[(t[(i + s1) % BC] >> 16) & 0xFF] ^ (tt >> 16)) & 0xFF) result.append((S[(t[(i + s2) % BC] >> 8) & 0xFF] ^ (tt >> 8)) & 0xFF) result.append((S[ t[(i + s3) % BC] & 0xFF] ^ tt ) & 0xFF) return string.join(map(chr, result), '') def decrypt(self, ciphertext): if len(ciphertext) != self.block_size: raise ValueError('wrong block length, expected ' + str(self.block_size) + ' got ' + str(len(plaintext))) Kd = self.Kd BC = self.block_size / 4 ROUNDS = len(Kd) - 1 if BC == 4: SC = 0 elif BC == 6: SC = 1 else: SC = 2 s1 = shifts[SC][1][1] s2 = shifts[SC][2][1] s3 = shifts[SC][3][1] a = [0] * BC # temporary work array t = [0] * BC # ciphertext to ints + key for i in xrange(BC): t[i] = (ord(ciphertext[i * 4 ]) << 24 | ord(ciphertext[i * 4 + 1]) << 16 | ord(ciphertext[i * 4 + 2]) << 8 | ord(ciphertext[i * 4 + 3]) ) ^ Kd[0][i] # apply round transforms for r in xrange(1, ROUNDS): for i in xrange(BC): a[i] = (T5[(t[ i ] >> 24) & 0xFF] ^ T6[(t[(i + s1) % BC] >> 16) & 0xFF] ^ T7[(t[(i + s2) % BC] >> 8) & 0xFF] ^ T8[ t[(i + s3) % BC] & 0xFF] ) ^ Kd[r][i] t = copy.copy(a) # last round is special result = [] for i in xrange(BC): tt = Kd[ROUNDS][i] result.append((Si[(t[ i ] >> 24) & 0xFF] ^ (tt >> 24)) & 0xFF) result.append((Si[(t[(i + s1) % BC] >> 16) & 0xFF] ^ (tt >> 16)) & 0xFF) result.append((Si[(t[(i + s2) % BC] >> 8) & 0xFF] ^ (tt >> 8)) & 0xFF) result.append((Si[ t[(i + s3) % BC] & 0xFF] ^ tt ) & 0xFF) return string.join(map(chr, result), '') def encrypt(key, block): return rijndael(key, len(block)).encrypt(block) def decrypt(key, block): return rijndael(key, len(block)).decrypt(block) def test(): def t(kl, bl): b = 'b' * bl r = rijndael('a' * kl, bl) assert r.decrypt(r.encrypt(b)) == b t(16, 16) t(16, 24) t(16, 32) t(24, 16) t(24, 24) t(24, 32) t(32, 16) t(32, 24) t(32, 32)