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chfast
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Jan 8, 2026
Using w=5 window size gives mixed results, probably depends on the scalar size.
│ o/ec-wnaf-4.txt │ o/ec-wnaf-5.txt │
│ gas/s │ gas/s vs base │
precompile<PrecompileId::ecrecover,_evmmax_cpp>-14 27.04M ± 0% 27.89M ± 2% +3.14% (p=0.000 n=11)
precompile<PrecompileId::ecmul,_evmmax_cpp>-14 128.1M ± 1% 125.6M ± 1% -1.99% (p=0.000 n=11)
precompile<PrecompileId::p256verify,_evmone_cpp>-14 64.30M ± 0% 66.38M ± 0% +3.23% (p=0.000 n=11)
geomean 60.62M 61.49M +1.43%
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Pull request overview
This PR replaces the Straus-Shamir multi-scalar multiplication (MSM) algorithm with a windowed Non-Adjacent Form (wNAF) method for elliptic curve cryptography operations, achieving ~13% performance improvement. The change introduces a NAF helper class for encoding scalars, implements wNAF recoding with a conservative window size of 4, and adds comprehensive unit tests for the NAF encoding/decoding functionality.
Key changes:
- Implemented wNAF-based MSM algorithm with precomputed lookup tables for odd multiples
- Added NAF class for storing and manipulating NAF representations
- Created unit tests covering various window sizes, edge cases, and fuzzing for uint256 values
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| test/unittests/crypto_wnaf.cpp | New unit tests for NAF encoding/decoding with comprehensive test cases including edge cases and fuzzing |
| test/unittests/CMakeLists.txt | Added crypto_wnaf.cpp to the test sources |
| lib/evmone_precompiles/ecc.hpp | Replaced Straus-Shamir MSM with wNAF-based implementation, added NAF class and helper functions |
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- Replace Straus-Shamir MSM with windowed NAF (sliding window) method. - Set conservative initial windows size w=4. - Add NAF helper class, wNAF recoding, and shared MSM utility. - Cover NAF encoding/decoding with new crypto_wnaf unit tests. ### Benchmark results ``` │ o/ec.txt │ o/ec-wnaf-4.txt │ │ sec/op │ sec/op vs base │ precompile<PrecompileId::ecrecover,_evmmax_cpp>-14 126.3μ ± 0% 111.0μ ± 0% -12.13% (p=0.001 n=11) precompile<PrecompileId::ecmul,_evmmax_cpp>-14 53.91μ ± 0% 46.83μ ± 0% -13.13% (p=0.000 n=11) precompile<PrecompileId::p256verify,_evmone_cpp>-14 124.4μ ± 90% 107.2μ ± 90% -13.83% (p=0.028 n=11) geomean 94.61μ 82.28μ -13.03% │ o/ec.txt │ o/ec-wnaf-4.txt │ │ gas/op │ gas/op vs base │ precompile<PrecompileId::ecrecover,_evmmax_cpp>-14 30.00k ± 0% 30.00k ± 0% ~ (p=1.000 n=11) 1 precompile<PrecompileId::ecmul,_evmmax_cpp>-14 60.00k ± 0% 60.00k ± 0% ~ (p=1.000 n=11) 1 precompile<PrecompileId::p256verify,_evmone_cpp>-14 69.00k ± 0% 69.00k ± 0% ~ (p=1.000 n=11) 1 geomean 49.89k 49.89k +0.00% 1 all samples are equal │ o/ec.txt │ o/ec-wnaf-4.txt │ │ gas/s │ gas/s vs base │ precompile<PrecompileId::ecrecover,_evmmax_cpp>-14 23.75M ± 0% 27.04M ± 0% +13.86% (p=0.000 n=11) precompile<PrecompileId::ecmul,_evmmax_cpp>-14 111.3M ± 0% 128.1M ± 1% +15.09% (p=0.000 n=11) precompile<PrecompileId::p256verify,_evmone_cpp>-14 55.39M ± 0% 64.30M ± 0% +16.09% (p=0.000 n=11) geomean 52.71M 60.62M +15.01% │ o/ec.txt │ o/ec-wnaf-4.txt │ │ cycles/op │ cycles/op vs base │ precompile<PrecompileId::ecrecover,_evmmax_cpp>-14 503.5k ± 1% 441.4k ± 0% -12.33% (p=0.000 n=11) precompile<PrecompileId::ecmul,_evmmax_cpp>-14 214.9k ± 0% 186.5k ± 0% -13.22% (p=0.000 n=11) precompile<PrecompileId::p256verify,_evmone_cpp>-14 495.8k ± 90% 427.4k ± 0% -13.79% (p=0.010 n=11) geomean 377.1k 327.7k -13.11% │ o/ec.txt │ o/ec-wnaf-4.txt │ │ instructions/op │ instructions/op vs base │ precompile<PrecompileId::ecrecover,_evmmax_cpp>-14 1.537M ± 0% 1.382M ± 0% -10.12% (p=0.000 n=11) precompile<PrecompileId::ecmul,_evmmax_cpp>-14 737.5k ± 0% 663.6k ± 0% -10.03% (p=0.000 n=11) precompile<PrecompileId::p256verify,_evmone_cpp>-14 1.552M ± 0% 1.386M ± 0% -10.74% (p=0.000 n=11) geomean 1.207M 1.083M -10.29% ```
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Jan 27, 2026
There is wNAF overflow bug, probably not discovered by ECC because we don't use max 256-bit scalar.
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