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# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
import binascii
import struct
from cryptography.hazmat.primitives import ciphers
from cryptography.hazmat.primitives.ciphers import algorithms
_N_BLOCKS = [1, 1.5, 2, 2.5, 3]
_INITIAL_COUNTERS = [2**32 - 1, 2**64 - 1]
def _build_vectors():
count = 0
output = []
key = "0" * 64
nonce = "0" * 16
for blocks in _N_BLOCKS:
plaintext = binascii.unhexlify("0" * int(128 * blocks))
for counter in _INITIAL_COUNTERS:
full_nonce = struct.pack("<Q", counter) + binascii.unhexlify(nonce)
cipher = ciphers.Cipher(
algorithms.ChaCha20(binascii.unhexlify(key), full_nonce),
None,
)
encryptor = cipher.encryptor()
output.append(f"\nCOUNT = {count}")
count += 1
output.append(f"KEY = {key}")
output.append(f"NONCE = {nonce}")
output.append(f"INITIAL_BLOCK_COUNTER = {counter}")
output.append(f"PLAINTEXT = {binascii.hexlify(plaintext)}")
output.append(
f"CIPHERTEXT = {binascii.hexlify(encryptor.update(plaintext))}"
)
return "\n".join(output)
def _write_file(data, filename):
with open(filename, "w") as f:
f.write(data)
if __name__ == "__main__":
_write_file(_build_vectors(), "counter-overflow.txt")
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