Feat/poseidon2

[ThomasPiellard]

Description

Implementation of poseidon2 for t=2,3 following
reference implementation
reference paper
TBD: algos 1, 2, 3 of https://tosc.iacr.org/index.php/ToSC/article/view/8913/8489 for finding internal matrices when t>3

see gnark-crypto's corresponding PR

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How has this been tested?

see TestPoseidon2, tested against gnark-crypto's implementation

How has this been benchmarked?

scs: 632 constraints for t=3
r1cs: 243 constraints for t=3

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I did not modify files generated from templates
• golangci-lint does not output errors locally
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[yelhousni]

LGTM! the PR follows Consensys/gnark-crypto#553 (review). Next we need to use poseidon2 in other places (commitment, recursion, signature, gkr...) and do some benchmarks.

[yelhousni]

should the branch be rebased on master?