Executing the unit tests for the bip324_cipher.py module currently
takes quite long (>60 seconds on my notebook). Most time here is spent
in empty plaintext/ciphertext encryption/decryption loops:
....
for _ in range(msg_idx):
enc_aead.encrypt(b"", b"")
...
for _ in range(msg_idx):
enc_aead.decrypt(b"", bytes(16))
...
Their sole purpose is increasing the FSChaCha20Poly1305 packet
counters in order to trigger rekeying, i.e. the actual
encryption/decryption is not relevant, as the result is thrown away.
This commit speeds up the tests by supporting to pass "None" as
plaintext/ciphertext, indicating to the routines that no actual
encryption/decryption should be done.
master branch:
$ python3 -m unittest ./test/functional/test_framework/crypto/bip324_cipher.py
..
----------------------------------------------------------------------
Ran 2 tests in 64.658s
PR branch:
$ python3 -m unittest ./test/functional/test_framework/crypto/bip324_cipher.py
..
----------------------------------------------------------------------
Ran 2 tests in 0.822s
