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| 1 | +# Pure Python AES encryption routines. |
| 2 | +# |
| 3 | +# AES is integer based and inplace so doesn't use the heap. It is therefore |
| 4 | +# a good test of raw performance and correctness of the VM/runtime. |
| 5 | +# |
| 6 | +# The AES code comes first (code originates from a C version authored by D.P.George) |
| 7 | +# and then the test harness at the bottom. |
| 8 | +# |
| 9 | +# MIT license; Copyright (c) 2016 Damien P. George on behalf of Pycom Ltd |
| 10 | + |
| 11 | +################################################################## |
| 12 | +# discrete arithmetic routines, mostly from a precomputed table |
| 13 | + |
| 14 | +# non-linear, invertible, substitution box |
| 15 | +aes_s_box_table = bytes(( |
| 16 | + 0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76, |
| 17 | + 0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0, |
| 18 | + 0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15, |
| 19 | + 0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75, |
| 20 | + 0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84, |
| 21 | + 0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf, |
| 22 | + 0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8, |
| 23 | + 0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2, |
| 24 | + 0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73, |
| 25 | + 0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb, |
| 26 | + 0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79, |
| 27 | + 0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08, |
| 28 | + 0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a, |
| 29 | + 0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e, |
| 30 | + 0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf, |
| 31 | + 0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16, |
| 32 | +)) |
| 33 | + |
| 34 | +# multiplication of polynomials modulo x^8 + x^4 + x^3 + x + 1 = 0x11b |
| 35 | +def aes_gf8_mul_2(x): |
| 36 | + if x & 0x80: |
| 37 | + return (x << 1) ^ 0x11b |
| 38 | + else: |
| 39 | + return x << 1 |
| 40 | + |
| 41 | +def aes_gf8_mul_3(x): |
| 42 | + return x ^ aes_gf8_mul_2(x) |
| 43 | + |
| 44 | +# non-linear, invertible, substitution box |
| 45 | +def aes_s_box(a): |
| 46 | + return aes_s_box_table[a & 0xff] |
| 47 | + |
| 48 | +# return 0x02^(a-1) in GF(2^8) |
| 49 | +def aes_r_con(a): |
| 50 | + ans = 1 |
| 51 | + while a > 1: |
| 52 | + ans <<= 1; |
| 53 | + if ans & 0x100: |
| 54 | + ans ^= 0x11b |
| 55 | + a -= 1 |
| 56 | + return ans |
| 57 | + |
| 58 | +################################################################## |
| 59 | +# basic AES algorithm; see FIPS-197 |
| 60 | + |
| 61 | +# all inputs must be size 16 |
| 62 | +def aes_add_round_key(state, w): |
| 63 | + for i in range(16): |
| 64 | + state[i] ^= w[i] |
| 65 | + |
| 66 | +# combined sub_bytes, shift_rows, mix_columns, add_round_key |
| 67 | +# all inputs must be size 16 |
| 68 | +def aes_sb_sr_mc_ark(state, w, w_idx, temp): |
| 69 | + temp_idx = 0 |
| 70 | + for i in range(4): |
| 71 | + x0 = aes_s_box_table[state[i * 4]] |
| 72 | + x1 = aes_s_box_table[state[1 + ((i + 1) & 3) * 4]] |
| 73 | + x2 = aes_s_box_table[state[2 + ((i + 2) & 3) * 4]] |
| 74 | + x3 = aes_s_box_table[state[3 + ((i + 3) & 3) * 4]] |
| 75 | + temp[temp_idx] = aes_gf8_mul_2(x0) ^ aes_gf8_mul_3(x1) ^ x2 ^ x3 ^ w[w_idx] |
| 76 | + temp[temp_idx + 1] = x0 ^ aes_gf8_mul_2(x1) ^ aes_gf8_mul_3(x2) ^ x3 ^ w[w_idx + 1] |
| 77 | + temp[temp_idx + 2] = x0 ^ x1 ^ aes_gf8_mul_2(x2) ^ aes_gf8_mul_3(x3) ^ w[w_idx + 2] |
| 78 | + temp[temp_idx + 3] = aes_gf8_mul_3(x0) ^ x1 ^ x2 ^ aes_gf8_mul_2(x3) ^ w[w_idx + 3] |
| 79 | + w_idx += 4 |
| 80 | + temp_idx += 4 |
| 81 | + for i in range(16): |
| 82 | + state[i] = temp[i] |
| 83 | + |
| 84 | +# combined sub_bytes, shift_rows, add_round_key |
| 85 | +# all inputs must be size 16 |
| 86 | +def aes_sb_sr_ark(state, w, w_idx, temp): |
| 87 | + temp_idx = 0 |
| 88 | + for i in range(4): |
| 89 | + x0 = aes_s_box_table[state[i * 4]] |
| 90 | + x1 = aes_s_box_table[state[1 + ((i + 1) & 3) * 4]] |
| 91 | + x2 = aes_s_box_table[state[2 + ((i + 2) & 3) * 4]] |
| 92 | + x3 = aes_s_box_table[state[3 + ((i + 3) & 3) * 4]] |
| 93 | + temp[temp_idx] = x0 ^ w[w_idx] |
| 94 | + temp[temp_idx + 1] = x1 ^ w[w_idx + 1] |
| 95 | + temp[temp_idx + 2] = x2 ^ w[w_idx + 2] |
| 96 | + temp[temp_idx + 3] = x3 ^ w[w_idx + 3] |
| 97 | + w_idx += 4 |
| 98 | + temp_idx += 4 |
| 99 | + for i in range(16): |
| 100 | + state[i] = temp[i] |
| 101 | + |
| 102 | +# take state as input and change it to the next state in the sequence |
| 103 | +# state and temp have size 16, w has size 16 * (Nr + 1), Nr >= 1 |
| 104 | +def aes_state(state, w, temp, nr): |
| 105 | + aes_add_round_key(state, w) |
| 106 | + w_idx = 16 |
| 107 | + for i in range(nr - 1): |
| 108 | + aes_sb_sr_mc_ark(state, w, w_idx, temp) |
| 109 | + w_idx += 16 |
| 110 | + aes_sb_sr_ark(state, w, w_idx, temp) |
| 111 | + |
| 112 | +# expand 'key' to 'w' for use with aes_state |
| 113 | +# key has size 4 * Nk, w has size 16 * (Nr + 1), temp has size 16 |
| 114 | +def aes_key_expansion(key, w, temp, nk, nr): |
| 115 | + for i in range(4 * nk): |
| 116 | + w[i] = key[i] |
| 117 | + w_idx = 4 * nk - 4 |
| 118 | + for i in range(nk, 4 * (nr + 1)): |
| 119 | + t = temp |
| 120 | + t_idx = 0 |
| 121 | + if i % nk == 0: |
| 122 | + t[0] = aes_s_box(w[w_idx + 1]) ^ aes_r_con(i // nk) |
| 123 | + for j in range(1, 4): |
| 124 | + t[j] = aes_s_box(w[w_idx + (j + 1) % 4]) |
| 125 | + elif nk > 6 and i % nk == 4: |
| 126 | + for j in range(0, 4): |
| 127 | + t[j] = aes_s_box(w[w_idx + j]) |
| 128 | + else: |
| 129 | + t = w |
| 130 | + t_idx = w_idx |
| 131 | + w_idx += 4 |
| 132 | + for j in range(4): |
| 133 | + w[w_idx + j] = w[w_idx + j - 4 * nk] ^ t[t_idx + j] |
| 134 | + |
| 135 | +################################################################## |
| 136 | +# simple use of AES algorithm, using output feedback (OFB) mode |
| 137 | + |
| 138 | +class AES: |
| 139 | + def __init__(self, keysize): |
| 140 | + if keysize == 128: |
| 141 | + self.nk = 4 |
| 142 | + self.nr = 10 |
| 143 | + elif keysize == 192: |
| 144 | + self.nk = 6 |
| 145 | + self.nr = 12 |
| 146 | + else: |
| 147 | + assert keysize == 256 |
| 148 | + self.nk = 8 |
| 149 | + self.nr = 14 |
| 150 | + |
| 151 | + self.state = bytearray(16) |
| 152 | + self.w = bytearray(16 * (self.nr + 1)) |
| 153 | + self.temp = bytearray(16) |
| 154 | + self.state_pos = 16 |
| 155 | + |
| 156 | + def set_key(self, key): |
| 157 | + aes_key_expansion(key, self.w, self.temp, self.nk, self.nr) |
| 158 | + self.state_pos = 16 |
| 159 | + |
| 160 | + def set_iv(self, iv): |
| 161 | + for i in range(16): |
| 162 | + self.state[i] = iv[i] |
| 163 | + self.state_pos = 16; |
| 164 | + |
| 165 | + def get_some_state(self, n_needed): |
| 166 | + if self.state_pos >= 16: |
| 167 | + aes_state(self.state, self.w, self.temp, self.nr) |
| 168 | + self.state_pos = 0 |
| 169 | + n = 16 - self.state_pos |
| 170 | + if n > n_needed: |
| 171 | + n = n_needed |
| 172 | + return n |
| 173 | + |
| 174 | + def apply_to(self, data): |
| 175 | + idx = 0 |
| 176 | + n = len(data) |
| 177 | + while n > 0: |
| 178 | + ln = self.get_some_state(n) |
| 179 | + n -= ln |
| 180 | + for i in range(ln): |
| 181 | + data[idx + i] ^= self.state[self.state_pos + i] |
| 182 | + idx += ln |
| 183 | + self.state_pos += n |
| 184 | + |
| 185 | +########################################################################### |
| 186 | +# Benchmark interface |
| 187 | + |
| 188 | +bm_params = { |
| 189 | + (50, 25): (1, 16), |
| 190 | + (100, 100): (1, 32), |
| 191 | + (1000, 1000): (4, 256), |
| 192 | + (5000, 1000): (20, 256), |
| 193 | +} |
| 194 | + |
| 195 | +def bm_setup(params): |
| 196 | + nloop, datalen = params |
| 197 | + |
| 198 | + aes = AES(256) |
| 199 | + key = bytearray(256 // 8) |
| 200 | + iv = bytearray(16) |
| 201 | + data = bytearray(datalen) |
| 202 | + # from now on we don't use the heap |
| 203 | + |
| 204 | + def run(): |
| 205 | + for loop in range(nloop): |
| 206 | + # encrypt |
| 207 | + aes.set_key(key) |
| 208 | + aes.set_iv(iv) |
| 209 | + for i in range(2): |
| 210 | + aes.apply_to(data) |
| 211 | + |
| 212 | + # decrypt |
| 213 | + aes.set_key(key) |
| 214 | + aes.set_iv(iv) |
| 215 | + for i in range(2): |
| 216 | + aes.apply_to(data) |
| 217 | + |
| 218 | + # verify |
| 219 | + for i in range(len(data)): |
| 220 | + assert data[i] == 0 |
| 221 | + |
| 222 | + def result(): |
| 223 | + return params[0] * params[1], True |
| 224 | + |
| 225 | + return run, result |
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