Add halo2 impl

[DanTehrani]

No description provided.

[DanTehrani]

Added halo2 impl!
The merge conflict is my bad, but it's an easy fix

If we mark halo2 stuff as WIP, merging and presenting the halo2 impl shouldn't be a problem

[RiverRuby]

@DanTehrani I wonder if we should still keep the circom benchmarks on the opening README? So people can quickly understand how useful the project is?

[RiverRuby]

LGTM as long as benchmarks end up on front page README, which seems like it'll be handled by the fork where we remove the extraneous PubkeyToAddress()

[DanTehrani]

@vb7401 Thanks for the review!
However I’m not really eager to merge this into main right now.

• The implementation is not complete, and there seems to be some interest in this repo, so we shouldn’t commit incomplete/uncertain things to main.
• We’re trying out different proving systems and other optimization, so we might completely discard the Halo2 impl in the near future.

wdyt?

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