IPA PoC

[arijitdutta67]

This PR implements a proof of concept version of the inner product argument (IPA) polynomial commitment scheme as in https://eprint.iacr.org/2019/1021.pdf. The spec for the implementation is in https://hackmd.io/q-A8y6aITWyWJrvsGGMWNA?view.

[zac-williamson]

I've left some comments describing future improvements.

The only action items before we merge are to remove the waffle namespace and to tidy up how L_elements and R_elements are populated (directly construct from partial_L and partial_R)

Once this is done I'm happy for the branch to be merged.

However I wouldn't consider this project truly complete until the following points are achieved:

1. commit, ipa_prove and ipa_verify take in an SRS object instead of a vector of generators (and have this SRS class load the required points from disk like our KZG SRS)
2. the SRS object contains a single pippenger_runtime_state object that is used to perform all pippenger computations (constructing pippenger_runtime_state is expensive)
3. the Fiat-Shamir heuristic is used to generate the round challenges as part of the ipa_prove and ipa_verify algorithms. The InnerProductArgument class should have a Hash template parameter that defines which hash algorithm is used.
4. methods are added that batch prove and batch verify multiple polynomial commitments

The above 4 points are required for the IPA commitment scheme to be used in a protocol like Honk or Plonk.