Compile Circuits

note

This guide is only useful if you need an specific configurations for number of users, votes, etc. If you plant to use the new circuits in production, make sure they go through a trusted ceremony.

Installation

Requirements

You need the following to generate new circuits:

• The rapidsnark tool if running on an intel chip (this allows for faster proof generation vs snarkjs).

note

MACI works on Linux and MacOS. It has not been tested on Windows, however it should work on Windows Subsystem for Linux (WSL). Keep in mind that when using MACI e2e on a non intel chip, tests will run using snarkjs with WASM. This will result in slower proof generation.

Install rapidsnark (if on an intel chip)

First, install dependencies:

sudo apt-get install build-essential cmake libgmp-dev libsodium-dev nasm curl m4

If you're running on MacOS with an intel chip, install dependencies by running the following command:

brew install cmake gmp libsodium nasm

Next, clone rapidsnark and build it:

git clone https://github.com/iden3/rapidsnark.git && \
cd rapidsnark

pnpm install && \
git submodule init && \
git submodule update && \
./build_gmp.sh host && \
mkdir build_prover && cd build_prover && \
cmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=../package && \
make -j4 && make install

Note the location of the rapidsnark binary (e.g. /home/user/rapidsnark/build/prover).

For more information, please check rapidsnark github repo

Install circom v2:

https://docs.circom.io/

Note the location of the circom binary (e.g. $HOME/.cargo/bin/circom), as you will need it later.

On Intel chips (no ARM64)

Install dependencies:

sudo apt-get install libgmp-dev nlohmann-json3-dev nasm g++

info

Remember that if on a ARM64 chip, you will not be able to compile the c++ witness generator and thus use rapidsnark. Please follow instructions for WASM artifacts, in case you decide to recompile artifacts.

Configure circomkit

Edit circuits/circom/circuits to include the circuits you would like to compile. This comes already configured with the three main circuits and with testing parameters:

{
  "ProcessMessages_10-2-1-2_test": {
    "file": "processMessages",
    "template": "ProcessMessages",
    "params": [10, 2, 1, 2],
    "pubs": [
      "numSignUps",
      "index",
      "batchEndIndex",
      "msgRoot",
      "currentSbCommitment",
      "newSbCommitment",
      "pollEndTimestamp",
      "actualStateTreeDepth",
      "coordinatorPublicKeyHash"
    ]
  },
  "ProcessMessagesNonQv_10-2-1-2_test": {
    "file": "processMessagesNonQv",
    "template": "ProcessMessagesNonQv",
    "params": [10, 2, 1, 2],
    "pubs": [
      "numSignUps",
      "index",
      "batchEndIndex",
      "msgRoot",
      "currentSbCommitment",
      "newSbCommitment",
      "pollEndTimestamp",
      "actualStateTreeDepth",
      "coordinatorPublicKeyHash"
    ]
  },
  "TallyVotes_10-1-2_test": {
    "file": "tallyVotes",
    "template": "TallyVotes",
    "params": [10, 1, 2],
    "pubs": ["index", "numSignUps", "sbCommitment", "currentTallyCommitment", "newTallyCommitment"]
  },
  "TallyVotesNonQv_10-1-2_test": {
    "file": "tallyVotesNonQv",
    "template": "TallyVotesNonQv",
    "params": [10, 1, 2],
    "pubs": ["index", "numSignUps", "sbCommitment", "currentTallyCommitment", "newTallyCommitment"]
  }
}

Generate .zkey files

If you wish to generate .zkey files from scratch, first navigate to circuits/circom and edit circuits.json. Set the parameters you need.

Next, run the following to compile the circuits with parameters you specified:

for the c++ witness generator

pnpm test:circuits-c -- --outPath ../cli/zkeys

for the wasm witness generator

pnpm build:circuits-wasm -- --outPath ../cli/zkeys

Finally, generate the .zkey files. This may require a lot of memory and time.

pnpm setup:zkeys -- --outPath ../cli/zkeys

If on a ARM64 chip, the above will work with the wasm witness only. The errors you will get for the c++ witness are:

main.cpp:9:10: fatal error: 'nlohmann/json.hpp' file not found
#include <nlohmann/json.hpp>
       ^~~~~~~~~~~~~~~~~~~
1 error generated.