Installing the circom ecosystem

⚠ Important deprecation note

The old circom compiler written in Javascript will be frozen, but it can still be downloaded from the old circom repository.

Installing dependencies

You need several dependencies in your system to run circom and its associated tools.

• The core tool is the circom compiler which is written in Rust. To have Rust available in your system, you can install rustup. If you’re using Linux or macOS, open a terminal and enter the following command:

curl --proto '=https' --tlsv1.2 https://sh.rustup.rs -sSf | sh

• We also distribute a series of npm packages so Node.js and some package manager like npm or yarn should be available in your system. Recent versions of Node.js include big integer support and web assembly compilers that help run code faster, so to get a better performance, install version 10 or higher.

Installing circom

To install from our sources, clone the circom repository:

git clone https://github.com/iden3/circom.git

Enter the circom directory and use the cargo build to compile:

cargo build --release

The installation takes around 3 minutes to be completed. When the command successfully finishes, it generates the circom binary in the directory target/release. You can install this binary as follows (Note: Make sure you're still in the circom directory when running this command) :

cargo install --path circom

The previous command will install the circom binary in the directory $HOME/.cargo/bin.

Now, you should be able to see all the options of the executable by using the help flag:

circom --help

circom compiler 2.2.2
IDEN3
Compiler for the circom programming language

USAGE:
    circom [FLAGS] [OPTIONS] [--] [input]

FLAGS:
        --r1cs                                 Outputs the constraints in r1cs format
        --sym                                  Outputs witness in sym format
        --wasm                                 Compiles the circuit to wasm
        --json                                 Outputs the constraints in json format
        --wat                                  Compiles the circuit to wat
    -c, --c                                    Compiles the circuit to C++
        --O0                                   No simplification is applied
        --O1                                   Only applies signal to signal and signal to constant simplification. This
                                               is the default option
        --O2                                   Full constraint simplification
        --verbose                              Shows logs during compilation
        --inspect                              Does an additional check over the constraints produced
        --constraint_assert_dissabled          Does not add asserts in the witness generation code to check constraints
                                               introduced with "==="
        --use_old_simplification_heuristics    Applies the old version of the heuristics when performing linear
                                               simplification
        --simplification_substitution          Outputs the substitution applied in the simplification phase in json
                                               format
        --no_asm                               Does not use asm files in witness generation code in C++
        --no_init                              Removes initializations to 0 of variables ("var") in the witness
                                               generation code
    -h, --help                                 Prints help information
    -V, --version                              Prints version information

OPTIONS:
    -o, --output <output>                    Path to the directory where the output will be written [default: .]
    -p, --prime <prime>                      To choose the prime number to use to generate the circuit. Receives the
                                             name of the curve (bn128, bls12377, bls12381, goldilocks, grumpkin, pallas,
                                             secq256r1, vesta) [default: bn128]
    -l <link_libraries>...                   Adds directory to library search path
        --O2round <simplification_rounds>    Maximum number of rounds of the simplification process

ARGS:
    <input>    Path to a circuit with a main component [default: ./circuit.circom]

Installing snarkjs

snarkjs is a npm package that contains code to generate and validate ZK proofs from the artifacts produced by circom.

You can install snarkjs with the following command:

npm install -g snarkjs