# Pure Python AES encryption routines. # # AES is integer based and inplace so doesn't use the heap. It is therefore # a good test of raw performance and correctness of the VM/runtime. # # The AES code comes first (code originates from a C version authored by D.P.George) # and then the test harness at the bottom. # # MIT license; Copyright (c) 2016 Damien P. George on behalf of Pycom Ltd ################################################################## # discrete arithmetic routines, mostly from a precomputed table # non-linear, invertible, substitution box aes_s_box_table = bytes( ( 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, ) ) # multiplication of polynomials modulo x^8 + x^4 + x^3 + x + 1 = 0x11b def aes_gf8_mul_2(x): if x & 0x80: return (x << 1) ^ 0x11B else: return x << 1 def aes_gf8_mul_3(x): return x ^ aes_gf8_mul_2(x) # non-linear, invertible, substitution box def aes_s_box(a): return aes_s_box_table[a & 0xFF] # return 0x02^(a-1) in GF(2^8) def aes_r_con(a): ans = 1 while a > 1: ans <<= 1 if ans & 0x100: ans ^= 0x11B a -= 1 return ans ################################################################## # basic AES algorithm; see FIPS-197 # all inputs must be size 16 def aes_add_round_key(state, w): for i in range(16): state[i] ^= w[i] # combined sub_bytes, shift_rows, mix_columns, add_round_key # all inputs must be size 16 def aes_sb_sr_mc_ark(state, w, w_idx, temp): temp_idx = 0 for i in range(4): x0 = aes_s_box_table[state[i * 4]] x1 = aes_s_box_table[state[1 + ((i + 1) & 3) * 4]] x2 = aes_s_box_table[state[2 + ((i + 2) & 3) * 4]] x3 = aes_s_box_table[state[3 + ((i + 3) & 3) * 4]] temp[temp_idx] = aes_gf8_mul_2(x0) ^ aes_gf8_mul_3(x1) ^ x2 ^ x3 ^ w[w_idx] temp[temp_idx + 1] = x0 ^ aes_gf8_mul_2(x1) ^ aes_gf8_mul_3(x2) ^ x3 ^ w[w_idx + 1] temp[temp_idx + 2] = x0 ^ x1 ^ aes_gf8_mul_2(x2) ^ aes_gf8_mul_3(x3) ^ w[w_idx + 2] temp[temp_idx + 3] = aes_gf8_mul_3(x0) ^ x1 ^ x2 ^ aes_gf8_mul_2(x3) ^ w[w_idx + 3] w_idx += 4 temp_idx += 4 for i in range(16): state[i] = temp[i] # combined sub_bytes, shift_rows, add_round_key # all inputs must be size 16 def aes_sb_sr_ark(state, w, w_idx, temp): temp_idx = 0 for i in range(4): x0 = aes_s_box_table[state[i * 4]] x1 = aes_s_box_table[state[1 + ((i + 1) & 3) * 4]] x2 = aes_s_box_table[state[2 + ((i + 2) & 3) * 4]] x3 = aes_s_box_table[state[3 + ((i + 3) & 3) * 4]] temp[temp_idx] = x0 ^ w[w_idx] temp[temp_idx + 1] = x1 ^ w[w_idx + 1] temp[temp_idx + 2] = x2 ^ w[w_idx + 2] temp[temp_idx + 3] = x3 ^ w[w_idx + 3] w_idx += 4 temp_idx += 4 for i in range(16): state[i] = temp[i] # take state as input and change it to the next state in the sequence # state and temp have size 16, w has size 16 * (Nr + 1), Nr >= 1 def aes_state(state, w, temp, nr): aes_add_round_key(state, w) w_idx = 16 for i in range(nr - 1): aes_sb_sr_mc_ark(state, w, w_idx, temp) w_idx += 16 aes_sb_sr_ark(state, w, w_idx, temp) # expand 'key' to 'w' for use with aes_state # key has size 4 * Nk, w has size 16 * (Nr + 1), temp has size 16 def aes_key_expansion(key, w, temp, nk, nr): for i in range(4 * nk): w[i] = key[i] w_idx = 4 * nk - 4 for i in range(nk, 4 * (nr + 1)): t = temp t_idx = 0 if i % nk == 0: t[0] = aes_s_box(w[w_idx + 1]) ^ aes_r_con(i // nk) for j in range(1, 4): t[j] = aes_s_box(w[w_idx + (j + 1) % 4]) elif nk > 6 and i % nk == 4: for j in range(0, 4): t[j] = aes_s_box(w[w_idx + j]) else: t = w t_idx = w_idx w_idx += 4 for j in range(4): w[w_idx + j] = w[w_idx + j - 4 * nk] ^ t[t_idx + j] ################################################################## # simple use of AES algorithm, using output feedback (OFB) mode class AES: def __init__(self, keysize): if keysize == 128: self.nk = 4 self.nr = 10 elif keysize == 192: self.nk = 6 self.nr = 12 else: assert keysize == 256 self.nk = 8 self.nr = 14 self.state = bytearray(16) self.w = bytearray(16 * (self.nr + 1)) self.temp = bytearray(16) self.state_pos = 16 def set_key(self, key): aes_key_expansion(key, self.w, self.temp, self.nk, self.nr) self.state_pos = 16 def set_iv(self, iv): for i in range(16): self.state[i] = iv[i] self.state_pos = 16 def get_some_state(self, n_needed): if self.state_pos >= 16: aes_state(self.state, self.w, self.temp, self.nr) self.state_pos = 0 n = 16 - self.state_pos if n > n_needed: n = n_needed return n def apply_to(self, data): idx = 0 n = len(data) while n > 0: ln = self.get_some_state(n) n -= ln for i in range(ln): data[idx + i] ^= self.state[self.state_pos + i] idx += ln self.state_pos += n ########################################################################### # Benchmark interface bm_params = { (50, 25): (1, 16), (100, 100): (1, 32), (1000, 1000): (4, 256), (5000, 1000): (20, 256), } def bm_setup(params): nloop, datalen = params aes = AES(256) key = bytearray(256 // 8) iv = bytearray(16) data = bytearray(datalen) # from now on we don't use the heap def run(): for loop in range(nloop): # encrypt aes.set_key(key) aes.set_iv(iv) for i in range(2): aes.apply_to(data) # decrypt aes.set_key(key) aes.set_iv(iv) for i in range(2): aes.apply_to(data) # verify for i in range(len(data)): assert data[i] == 0 def result(): return params[0] * params[1], True return run, result