Groth16 prover written in Nim

This is Groth16 prover implementation in Nim, using the constantine library as an arithmetic / curve backend.

The implementation is compatible with the circom ecosystem.

At the moment only the BN254 (aka. alt-bn128) curve is supported.

TODO

• make it a nimble package
• proper MSM implementation (I couldn't make constantine's one to work)
• compare .r1cs to the "coeffs" section of .zkey
• generate fake circuit-specific setup ourselves
• multithreaded support (MSM, and possibly also FFT)
• add Groth16 notes
• document the snarkjs circuit-specific setup H points convention
• make it work for different curves