test: speedup bip324_cipher.py unit test #29390

Executing the unit tests for the bip324_cipher.py module currently takes quite long (>60 seconds on my older notebook). Most time here is spent in empty plaintext/ciphertext encryption/decryption loops in test_fschacha20poly1305aead:

https://github.com/bitcoin/bitcoin/blob/9eeee7caa3f95ee17a645e12d330261f8e3c2dbf/test/functional/test_framework/crypto/bip324_cipher.py#L193-L194 https://github.com/bitcoin/bitcoin/blob/9eeee7caa3f95ee17a645e12d330261f8e3c2dbf/test/functional/test_framework/crypto/bip324_cipher.py#L198-L199

Their sole purpose is increasing the FSChaCha20Poly1305 packet counter 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.

The approach here is a bit hacky, a cleaner alternative would probably be to introduce a special seek/skip_packets method and not touch the encrypt/decrypt routines, but that seemed overkill to me only for speeding up a unit test. Open for suggestions.

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

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Is this pull request associated with one of the issues at https://github.com/bitcoin/bitcoin/issues?

Concept ACK a8c3454

To run the individual test I had to run it from the test/functional directory this way: python3 -m unittest ./crypto/bip324_cipher.py

Saves about 10 seconds in test_runner on my machine

Before:

Running Unit Tests for Test Framework Modules
.....................
----------------------------------------------------------------------
Ran 21 tests in 15.701s

After:

Running Unit Tests for Test Framework Modules
.....................
----------------------------------------------------------------------
Ran 21 tests in 4.984s

a cleaner alternative would probably be to introduce a special seek/skip_packets method and not touch the encrypt/decrypt routines

Why did you choose this approach rather than adding a seek/skip_packet method?

Why did you choose this approach rather than adding a seek/skip_packet method? @epiccurious he explained in the very next line:

that seemed overkill to me only for speeding up a unit test. Open for suggestions

Tested ACK a8c3454ba137dfac20b3c89bc558374de0524114.

Before (commit 9eeee7caa3f95ee17a645e12d330261f8e3c2dbf):

Ran 2 tests in 15.541s

After:

Ran 2 tests in 0.204s

ACK a8c3454ba137dfac20b3c89bc558374de0524114. The comments at the top of bip324_cipher.py specify that this should only be used for testing, so I think this optimization makes sense in that context.

Before:

Ran 2 tests in 8.512s

After:

Ran 2 tests in 0.106s

ACK a8c3454!

ACK a8c3454. I think it's worth it because of the significant speedup in the unit test. @theStack, do you get negligible speedup in other v2 tests too? Maybe these negligible benchmarks aren't reliable but I somehow imagined there to be a very negligible slowdown because of an extra check.

1. unit test went from 10.807s to 0.16s
2. test/functional/p2p_v2_encrypted.py went from 7.266s to 5.766s
3. test_runner.py in #29358 went from 1135s to 1125s

cc @sipa

ACK a8c3454ba137dfac20b3c89bc558374de0524114