`engine-modexp` bug fixes and performance improvements - Githubissues

aurora-is-near / aurora-engine

⚙️ Aurora Engine implements an Ethereum Virtual Machine (EVM) on the NEAR Protocol.

https://doc.aurora.dev/develop/compat/evm

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`engine-modexp` bug fixes and performance improvements #809

Closed guidovranken closed 1 year ago

guidovranken commented 1 year ago

Description

This fixes the following issues with engine-modexp:

addition overflow in big_sq that would lead to incorrect output (and a crash in debug mode)
assert failure in sub_to_same_size that would lead to incorrect output
slow modular exponentiation with even modulus. The bottleneck was the routine were the inverse of A mod M was computed, where M is a power of two. This inversion function has been replaced with the algorithm found in this paper, which is much faster.

Performance / NEAR gas cost considerations

The performance of modular exponentiation with even modulus is improved. Performance remains the same for odd modulus.

Testing

Extensive fuzz testing, was was also the method used to detect the issues that this PR addresses.

How should this be reviewed

Additional information

joshuajbouw commented 1 year ago

I believe the cargo fmt is failing due to the use of nightly cargo fmt check in the CI.

aleksuss commented 1 year ago

@joshuajbouw no. We have pretty old nightly in our CI so it should be fixed, I guess.