What was wrong?

Fixes #71. I will use "BLS chia" as the alias of Chia network's BLS implementation, along with its python bindings in the following paragraphs.

How was it fixed?

• Implement functions sign, privtopub, verify, aggregate_signatures, aggregate_pubkeys, aggregate_multiple with BLS chia.
• Copy and modify the related tests from tests/test_bls.py to tests/test_bls_chia.py and test with those functions.
• Add a benchmark script scripts/benchmark_api.py, which is mostly inspired by Benchmark #69.

Problems

• The private key range in BLS chia seems to be different from py_ecc. Its range is [1, 2**32 - 1]. Therefore I currently workaround it through adding all private keys with 1.
• Sometimes signature aggregation throws RuntimeError: Caught an unknown exception! if the source signatures are initialized with blspy.Signature.from_bytes. This issue is really hard to debug since no further information is printed from the C++ side. Currently, I workaround it through adding a _sig_map: Dict[bytes, bls_chia.Signature] = {}, which memoizes all signatures generated through sign and aggregate_signatures, to avoid the issue resulting from Signature.from_bytes. Ref: Potential bug in Signature deserialization and aggregation using Python Chia-Network/bls-signatures#54

Example benchmark

Run number=100 times with timeit, with 20 keys and signatures aggregated. Need to further try the other parameters, and understand the meanings of the result.

# BLS chia
$ python py_ecc/scripts/benchmark_api.py bls_chia
Module py_ecc.bls_chia.api
privtopub: 0.012366111972369254
verify: 0.39142126898514107
aggregate_signatures: 2.8922514080186374
aggregate_pubkeys: 0.5968314119963907
verify_multiple: 4.292670964030549

# py_ecc itself
$ python py_ecc/scripts/benchmark_api.py bls
Module py_ecc.bls.api
privtopub: 1.719821373000741
verify: 121.40623104997212
aggregate_signatures: 31.77455569698941
aggregate_pubkeys: 1.140943904989399
verify_multiple: 763.4154342580005

To make use of the script with custom implementations:

• Implement api.py with functions privtopub, verify, aggregate_signatures, aggregate_pubkeys, verify_multiple.
• Put api.py under a package with your custom name, says "bls_another", under py_ecc, so py_ecc/bls_another/api.py.
• Run python py_ecc/scripts/benchmark_api.py bls_another.

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