Integrate witnesscalc/rapidsnark stack

[vivianjeng]

Problem

The latest rapidsnark works much faster than the current mopro stack (rust-witness + ark-works)

See: iden3/rapidsnark#27
It improves the loading zkey time in groth16prove

The benchmark is listed here: https://zkmopro.org/docs/performance/
We should spend more time explore this solution in mopro
to make it easier for developers to integrate witnesscalc, rapidsnark in their apps

Details

witnesscalc

• here we use https://github.com/0xPolygonID/witnesscalc
• It is written in CPP
• It works with RSA circuits
• It takes the .cpp file and the .dat file from circom circuit.circom -c
• developers have to manually specify two CMakeLists.txts to specify the circuit name
  1. CMakeLists.txt
  2. src/CMakeLists.txt
• Then developers can follow the readme to build the binaries
  • to build a xcframework for iOS, see this https://github.com/ulag/witnesscalc/blob/main/build_witnesscalc.sh
• each function/binding depends on the circuit (e.g. witnesscalc_authV2, witnesscalc_credentialAtomicQueryMTPV2,...)
  • (maybe we can try to improve this as well)
• then developers need to specify the bridge to let swift code or kotlin code to execute witnesscalc functions
  • iOS: See https://github.com/zkmopro/android-benchmark-app/pull/4/files
  • Android: See https://github.com/zkmopro/android-benchmark-app/pull/1/files

rapidsnark

• here we use https://github.com/iden3/rapidsnark
• It is written in CPP
• It works for all circuits when given zkey, wtns

Steps

1. Try to integrate in mopro with tools like https://github.com/dtolnay/cxx
   • pros:
     • we can easily switch adapter with different feature flag (e.g. circom-ark-works, circom-rapidsnark)
     • it can be called in other projects if written in Rust (e.g. it can be imported like rapidsnark = "0.1.0" in .toml)
2. (If we cannot integrate in Rust) Try to use mopro CLI to generate bindings for iOS and Android
   1. Read user specified circuit (the .cpp output and .dat file)
   2. We need to change the CMakeLists.txt to specify the circuit
      e.g. for circuit called cncircuit

      # cncircuit
      set(CNUB_SOURCES ${LIB_SOURCES}
        cncircuit.cpp
        witnesscalc_cncircuit.h
        witnesscalc_cncircuit.cpp
       )
                
       add_library(witnesscalc_cncircuit SHARED ${CNUB_SOURCES})
       add_library(witnesscalc_cncircuitStatic STATIC ${CNUB_SOURCES})
       set_target_properties(witnesscalc_cncircuitStatic PROPERTIES OUTPUT_NAME witnesscalc_cncircuit)

   3. build the library and xcframework (i-iii will be used in mopro build)
      See build_witnesscalc.sh file
   4. build template for witnesscalc/rapidsnark stack (will be used in mopro create)
      See https://github.com/zkmopro/android-benchmark-app
3. Update documentation
   • Current witnesscalc/rapidsnark stack is not trivial for developers to integrate in iOS/Android
   • We should document this steps or record in a video and shard on YouTube

Acceptance criteria

It can be in several PRs

1. A script to build witnesscalc frameworks with custom circuits (e.g. multiplier2, keccak256)
2. Tests to call the witnesscalc and rapidsnark in Rust (mopro-ffi)
3. If it can be called in Rust, try to build bindings with current mopro e.g.cargo run --bin ios in test-e2e
4. Add new adapter for mopro build commend (e.g.rapidsnark)
5. Add new platform for mopro create commend (e.g. rapidsnark)
6. Update documentation: in setup/rapidsnark setup

Next steps (optional)

If it works well we can remove the ark-works stack