Installation

Requirements

You need the following to use MACI:

• Node.js: use nvm to install it. MACI has been tested with Node 14, 16, 18 and 20. We do however recommend to use Node 18 or Node 20 as Node 14 is deprecated and Node 16 will soon be deprecated too.
• The rapidsnark tool if running on an intel chip (this allows for faster proof generation vs snarkjs).

Note that 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.

Installation

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.

Install MACI

git clone https://github.com/privacy-scaling-explorations/maci.git && \
cd maci && \
pnpm i && \
pnpm run build

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.

Decide whether you need to compile new circuits or use the test ones

If you are going to be making any changes to the circom circuits, then the following will apply to you. Otherwise, you can skip to the Download .zkey files section.

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": ["inputHash"]
  },
  "ProcessMessagesNonQv_10-2-1-2_test": {
    "file": "processMessagesNonQv",
    "template": "ProcessMessagesNonQv",
    "params": [10, 2, 1, 2],
    "pubs": ["inputHash"]
  },
  "TallyVotes_10-1-2_test": {
    "file": "tallyVotes",
    "template": "TallyVotes",
    "params": [10, 1, 2],
    "pubs": ["inputHash"]
  },
  "TallyVotesNonQv_10-1-2_test": {
    "file": "tallyVotesNonQv",
    "template": "TallyVotesNonQv",
    "params": [10, 1, 2],
    "pubs": ["inputHash"]
  }
}

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

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.

Download .zkey files (if you would like to use the default parameters or the trusted setup artifacts)

MACI has two main zk-SNARK circuits (plus an optional Subsidy circuit). Each circuit is parameterised. There should be one .zkey file for each circuit and set of parameters.

Unless you wish to generate a fresh set of .zkey files, you should obtain them from someone who has performed a multi-party trusted setup for said circuits. For more details on which artifacts have undergone a trusted setup, please refer to the Trusted Setup page.

Note the locations of the .zkey files as the CLI requires them as command-line flags.

Download test artifacts

pnpm download:test-zkeys

Download ceremony artifacts

pnpm download:ceremony-zkeys