File size: 10,927 Bytes
dfec228 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 |
import bchlib
import numpy as np
from typing import List, Tuple
import random
from copy import deepcopy
class RSC(object):
def __init__(self, data_bytes=16, ecc_bytes=4, verbose=False, **kwargs):
from reedsolo import RSCodec
self.rs = RSCodec(ecc_bytes)
if verbose:
print(f'Reed-Solomon ECC len: {ecc_bytes*8} bits')
self.data_len = data_bytes
self.dlen = data_bytes * 8 # data length in bits
self.ecc_len = ecc_bytes * 8 # ecc length in bits
def get_total_len(self):
return self.dlen + self.ecc_len
def encode_text(self, text: List[str]):
return np.array([self._encode_text(t) for t in text])
def _encode_text(self, text: str):
text = text + ' ' * (self.dlen // 8 - len(text))
out = self.rs.encode(text.encode('utf-8')) # bytearray
out = ''.join(format(x, '08b') for x in out) # bit string
out = np.array([int(x) for x in out], dtype=np.float32)
return out
def decode_text(self, data: np.array):
assert len(data.shape)==2
return [self._decode_text(d) for d in data]
def _decode_text(self, data: np.array):
assert len(data.shape)==1
data = ''.join([str(int(bit)) for bit in data])
data = bytes(int(data[i: i + 8], 2) for i in range(0, len(data), 8))
data = bytearray(data)
try:
data = self.rs.decode(data)[0]
data = data.decode('utf-8').strip()
except:
print('Error: Decode failed')
data = get_random_unicode(self.get_total_len()//8)
return data
def get_random_unicode(length):
# Update this to include code point ranges to be sampled
include_ranges = [
( 0x0021, 0x0021 ),
( 0x0023, 0x0026 ),
( 0x0028, 0x007E ),
( 0x00A1, 0x00AC ),
( 0x00AE, 0x00FF ),
( 0x0100, 0x017F ),
( 0x0180, 0x024F ),
( 0x2C60, 0x2C7F ),
( 0x16A0, 0x16F0 ),
( 0x0370, 0x0377 ),
( 0x037A, 0x037E ),
( 0x0384, 0x038A ),
( 0x038C, 0x038C ),
]
alphabet = [
chr(code_point) for current_range in include_ranges
for code_point in range(current_range[0], current_range[1] + 1)
]
return ''.join(random.choice(alphabet) for i in range(length))
class BCH(object):
def __init__(self, BCH_POLYNOMIAL = 137, BCH_BITS = 5, payload_len=100, verbose=True,**kwargs):
self.bch = bchlib.BCH(BCH_POLYNOMIAL, BCH_BITS)
self.payload_len = payload_len # in bits
self.data_len = (self.payload_len - self.bch.ecc_bytes*8)//7 # in ascii characters
assert self.data_len*7+self.bch.ecc_bytes*8 <= self.bch.n, f'Error! BCH with poly {BCH_POLYNOMIAL} and bits {BCH_BITS} can only encode max {self.bch.n//8} bytes of total payload'
if verbose:
print(f'BCH: POLYNOMIAL={BCH_POLYNOMIAL}, protected bits={BCH_BITS}, payload_len={payload_len} bits, data_len={self.data_len*7} bits ({self.data_len} ascii chars), ecc len={self.bch.ecc_bytes*8} bits')
def get_total_len(self):
return self.payload_len
def encode_text(self, text: List[str]):
return np.array([self._encode_text(t) for t in text])
def _encode_text(self, text: str):
text = text + ' ' * (self.data_len - len(text))
# data = text.encode('utf-8') # bytearray
data = encode_text_ascii(text) # bytearray
ecc = self.bch.encode(data) # bytearray
packet = data + ecc # payload in bytearray
packet = ''.join(format(x, '08b') for x in packet)
packet = [int(x) for x in packet]
packet.extend([0]*(self.payload_len - len(packet)))
packet = np.array(packet, dtype=np.float32)
return packet
def decode_text(self, data: np.array):
assert len(data.shape)==2
return [self._decode_text(d) for d in data]
def _decode_text(self, packet: np.array):
assert len(packet.shape)==1
packet = ''.join([str(int(bit)) for bit in packet]) # bit string
packet = packet[:(len(packet)//8*8)] # trim to multiple of 8 bits
packet = bytes(int(packet[i: i + 8], 2) for i in range(0, len(packet), 8))
packet = bytearray(packet)
# assert len(packet) == self.data_len + self.bch.ecc_bytes
data, ecc = packet[:-self.bch.ecc_bytes], packet[-self.bch.ecc_bytes:]
data0 = decode_text_ascii(deepcopy(data)).strip()
bitflips = self.bch.decode_inplace(data, ecc)
if bitflips == -1: # error, return random text
data = data0
else:
# data = data.decode('utf-8').strip()
data = decode_text_ascii(data).strip()
return data
def encode_text_ascii(text: str):
# encode text to 7-bit ascii
# input: text, str
# output: encoded text, bytearray
text_int7 = [ord(t) & 127 for t in text]
text_bitstr = ''.join(format(t,'07b') for t in text_int7)
if len(text_bitstr) % 8 != 0:
text_bitstr = '0'*(8-len(text_bitstr)%8) + text_bitstr # pad to multiple of 8
text_int8 = [int(text_bitstr[i:i+8], 2) for i in range(0, len(text_bitstr), 8)]
return bytearray(text_int8)
def decode_text_ascii(text: bytearray):
# decode text from 7-bit ascii
# input: text, bytearray
# output: decoded text, str
text_bitstr = ''.join(format(t,'08b') for t in text) # bit string
pad = len(text_bitstr) % 7
if pad != 0: # has padding, remove
text_bitstr = text_bitstr[pad:]
text_int7 = [int(text_bitstr[i:i+7], 2) for i in range(0, len(text_bitstr), 7)]
text_bytes = bytes(text_int7)
return text_bytes.decode('utf-8')
class ECC(object):
def __init__(self, BCH_POLYNOMIAL = 137, BCH_BITS = 5, **kwargs):
self.bch = bchlib.BCH(BCH_POLYNOMIAL, BCH_BITS)
def get_total_len(self):
return 100
def _encode(self, x):
# x: 56 bits, {0, 1}, np.array
# return: 100 bits, {0, 1}, np.array
dlen = len(x)
data_str = ''.join(str(x) for x in x.astype(int))
packet = bytes(int(data_str[i: i + 8], 2) for i in range(0, dlen, 8))
packet = bytearray(packet)
ecc = self.bch.encode(packet)
packet = packet + ecc # 96 bits
packet = ''.join(format(x, '08b') for x in packet)
packet = [int(x) for x in packet]
packet.extend([0, 0, 0, 0])
packet = np.array(packet, dtype=np.float32) # 100
return packet
def _decode(self, x):
# x: 100 bits, {0, 1}, np.array
# return: 56 bits, {0, 1}, np.array
packet_binary = "".join([str(int(bit)) for bit in x])
packet = bytes(int(packet_binary[i: i + 8], 2) for i in range(0, len(packet_binary), 8))
packet = bytearray(packet)
data, ecc = packet[:-self.bch.ecc_bytes], packet[-self.bch.ecc_bytes:]
bitflips = self.bch.decode_inplace(data, ecc)
if bitflips == -1: # error, return random data
data = np.random.binomial(1, .5, 56)
else:
data = ''.join(format(x, '08b') for x in data)
data = np.array([int(x) for x in data], dtype=np.float32)
return data # 56 bits
def _generate(self):
dlen = 56
data= np.random.binomial(1, .5, dlen)
packet = self._encode(data)
return packet, data
def generate(self, nsamples=1):
# generate random 56 bit secret
data = [self._generate() for _ in range(nsamples)]
data = (np.array([d[0] for d in data]), np.array([d[1] for d in data]))
return data # data with ecc, data org
def _to_text(self, data):
# data: {0, 1}, np.array
# return: str
data = ''.join([str(int(bit)) for bit in data])
all_bytes = [ data[i: i+8] for i in range(0, len(data), 8) ]
text = ''.join([chr(int(byte, 2)) for byte in all_bytes])
return text.strip()
def _to_binary(self, s):
if isinstance(s, str):
out = ''.join([ format(ord(i), "08b") for i in s ])
elif isinstance(s, bytes):
out = ''.join([ format(i, "08b") for i in s ])
elif isinstance(s, np.ndarray) and s.dtype is np.dtype(bool):
out = ''.join([chr(int(i)) for i in s])
elif isinstance(s, int) or isinstance(s, np.uint8):
out = format(s, "08b")
elif isinstance(s, np.ndarray):
out = [ format(i, "08b") for i in s ]
else:
raise TypeError("Type not supported.")
return np.array([float(i) for i in out], dtype=np.float32)
def _encode_text(self, s):
s = s + ' '*(7-len(s)) # 7 chars
s = self._to_binary(s) # 56 bits
packet = self._encode(s) # 100 bits
return packet, s
def encode_text(self, secret_list, return_pre_ecc=False):
"""encode secret with BCH ECC.
Input: secret (list of strings)
Output: secret (np array) with shape (B, 100) type float23, val {0,1}"""
assert np.all(np.array([len(s) for s in secret_list]) <= 7), 'Error! all strings must be less than 7 characters'
secret_list = [self._encode_text(s) for s in secret_list]
ecc = np.array([s[0] for s in secret_list], dtype=np.float32)
if return_pre_ecc:
return ecc, np.array([s[1] for s in secret_list], dtype=np.float32)
return ecc
def decode_text(self, data):
"""Decode secret with BCH ECC and convert to string.
Input: secret (torch.tensor) with shape (B, 100) type bool
Output: secret (B, 56)"""
data = self.decode(data)
data = [self._to_text(d) for d in data]
return data
def decode(self, data):
"""Decode secret with BCH ECC and convert to string.
Input: secret (torch.tensor) with shape (B, 100) type bool
Output: secret (B, 56)"""
data = data[:, :96]
data = [self._decode(d) for d in data]
return np.array(data)
def test_ecc():
ecc = ECC()
batch_size = 10
secret_ecc, secret_org = ecc.generate(batch_size) # 10x100 ecc secret, 10x56 org secret
# modify secret_ecc
secret_pred = secret_ecc.copy()
secret_pred[:,3:6] = 1 - secret_pred[:,3:6]
# pass secret_ecc to model and get predicted as secret_pred
secret_pred_org = ecc.decode(secret_pred) # 10x56
assert np.all(secret_pred_org == secret_org) # 10
def test_bch():
# test 100 bit
def check(text, poly, k, l):
bch = BCH(poly, k, l)
# text = 'secrets'
encode = bch.encode_text([text])
for ind in np.random.choice(l, k):
encode[0, ind] = 1 - encode[0, ind]
text_recon = bch.decode_text(encode)[0]
assert text==text_recon
check('secrets', 137, 5, 100)
check('some secret', 285, 10, 160)
if __name__ == '__main__':
test_ecc()
test_bch() |