| # Authors: |
| # Bram Cohen |
| # Trevor Perrin - various changes |
| # |
| # See the LICENSE file for legal information regarding use of this file. |
| # Also see Bram Cohen's statement below |
| |
| """ |
| 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 |
| |
| 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 range(255): |
| j = (alog[-1] << 1) ^ alog[-1] |
| if j & 0x100 != 0: |
| j ^= 0x11B |
| alog.append(j) |
| |
| log = [0] * 256 |
| for i in range(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 range(256)] |
| box[1][7] = 1 |
| for i in range(2, 256): |
| j = alog[255 - log[i]] |
| for t in range(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 range(256)] |
| for i in range(256): |
| for t in range(8): |
| cox[i][t] = B[t] |
| for j in range(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 range(256): |
| S[i] = cox[i][0] << 7 |
| for t in range(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 range(4)] |
| |
| for i in range(4): |
| for j in range(4): |
| AA[i][j] = G[i][j] |
| AA[i][i+4] = 1 |
| |
| for i in range(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 range(8): |
| AA[i][j], AA[t][j] = AA[t][j], AA[i][j] |
| pivot = AA[i][i] |
| for j in range(8): |
| if AA[i][j] != 0: |
| AA[i][j] = alog[(255 + log[AA[i][j] & 0xFF] - log[pivot & 0xFF]) % 255] |
| for t in range(4): |
| if i != t: |
| for j in range(i+1, 8): |
| AA[t][j] ^= mul(AA[i][j], AA[t][i]) |
| AA[t][i] = 0 |
| |
| iG = [[0] * 4 for i in range(4)] |
| |
| for i in range(4): |
| for j in range(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 range(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 range(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 range(ROUNDS + 1)] |
| # decryption round keys |
| Kd = [[0] * BC for i in range(ROUNDS + 1)] |
| ROUND_KEY_COUNT = (ROUNDS + 1) * BC |
| KC = len(key) // 4 |
| |
| # copy user material bytes into temporary ints |
| tk = [] |
| for i in range(0, KC): |
| tk.append((key[i * 4] << 24) | (key[i * 4 + 1] << 16) | |
| (key[i * 4 + 2] << 8) | 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 range(1, KC): |
| tk[i] ^= tk[i-1] |
| else: |
| for i in range(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 range(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 range(1, ROUNDS): |
| for j in range(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 range(BC): |
| t.append((plaintext[i * 4 ] << 24 | |
| plaintext[i * 4 + 1] << 16 | |
| plaintext[i * 4 + 2] << 8 | |
| plaintext[i * 4 + 3] ) ^ Ke[0][i]) |
| # apply round transforms |
| for r in range(1, ROUNDS): |
| for i in range(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 range(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 bytearray(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 range(BC): |
| t[i] = (ciphertext[i * 4 ] << 24 | |
| ciphertext[i * 4 + 1] << 16 | |
| ciphertext[i * 4 + 2] << 8 | |
| ciphertext[i * 4 + 3] ) ^ Kd[0][i] |
| # apply round transforms |
| for r in range(1, ROUNDS): |
| for i in range(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 range(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 bytearray(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) |
| |
