Example of circuit which verifies signature of message by provided public key

Prerequisites

• Rust (latest stable)
• Circom
• Node.js (latest stable)
• NPM (latest stable)

Circom installation

git clone https://github.com/iden3/circom.git cd circom && cargo build --release && cargo install --path circom

Installation

Update required submodules

git submodule update --init --recursive

Install required packages

cd circom-ecdsa && npm install && cd .. && npm install

Preparation

Required files

Prepare PowerOfTau Ceremony

Minimum required power for .ptau file is 21 (verify.circom has ~1.5m constraints).

Custom .ptau file

Howto prepare .ptau file could be found in guide here https://github.com/iden3/snarkjs starting from Step 1 to Step 8 (inclusive)

Pre-built .ptau file

Pre-built final .ptau files could be found in NOTE section right after Step 7

Compile circuit

Howto compile circuit could be found in guide here https://github.com/iden3/snarkjs in Step 10

Prepare .zkey file

Howto prepare .zkey file and export it to .json file could be found in guide here https://github.com/iden3/snarkjs starting from Step 15 to Step 22 (inclusive). This example currently supports only Groth16 proving system.

Usage

Run

npm start -- --message="%MESSAGE%" --gen-random-wallet --circuit %CIRCUIT_WASM_PATH% --zkey %ZKEY_PATH% --vkey %VERIFICATION_KEY_PATH%

where:

• %MESSAGE%: any message which should be signed and verified
• %CIRCUIT_WASM_PATH%: path to built circuit .wasm file
• %ZKEY_PATH%: path to prepared .zkey file (could be created during PowersOfTau Ceremony)
• %VERIFICATION_KEY_PATH%: path to exported verification key file in JSON format (should be exported from .zkey file)

Supported command line arguments

• --message: provides any text message for signing and verification
• --gen-random-wallet: generates etherium wallet randomly to be used later for signing
• --use-phrase: creates wallet using provided words phrase
• --circuit: path to compiled circuit .wasm file (usually located at ./verify_js/ directory)
• --zkey: path to prepared .zkey file
• --vkey: path to exported verification key file (could be exported from .zkey file by using snarkjs)

Run a test

npm test