gnark

gnark is a framework to execute (and verify) algorithms in zero-knowledge. It offers a high-level API to easily design circuits and fast implementation of state of the art ZKP schemes.

gnark has not been audited and is provided as-is, use at your own risk. In particular, gnark makes no security guarantees such as constant time implementation or side-channel attack resistance.

Proving systems

• Groth16

Curves

• BLS377
• BLS381
• BN256

Getting started

Prerequisites

gnark is optimized for Unix (Linux / macOS) 64bits platforms (and not tested on other architectures). You'll need to install Go.

Install gnark

Command line interface

go install github.com/ConsenSys/gnark

Library

go get github.com/ConsenSys/gnark

To install for use as a Go package:

go get github.com/consensys/gnark/cs

Workflow

Our blog post is a good place to start. In short:

1. Implement the algorithm using our API (written in Go)
2. Serialize the circuit in its R1CS form (circuit.r1cs) (in the examples/cubic subfolder, that would be go run examples/cubic/cubic.go)
3. Run gnark setup circuit.r1cs to generate proving and verifying keys
4. Run gnark prove circuit.r1cs --pk circuit.pk --input inputto generate a proof
5. Run gnark verify circuit.proof --vk circuit.vk --input input.public to verify a proof

Note that, currently, the input file has a simple csv-like format:

secret, x, 3
public, y, 35

Using the gnark CLI tool is optional. Developers may expose circuits through gRPC or REST APIs, export to Solidity, chose their serialization formats, etc. This is ongoing work on our side, but new feature suggestions or PR are welcome.

Examples and gnark usage

Examples are located in /examples.

Run gnark --help for a list of available commands.

/examples/cubic_equation

// x**3 + x + 5  y
func main() {
	// create root constraint system
	circuit := cs.New()

	// declare secret and public inputs
	x := circuit.SECRET_INPUT("x")
	y := circuit.PUBLIC_INPUT("y")

	// specify constraints
	x3 := circuit.MUL(x, x, x)
	circuit.MUSTBE_EQ(y, circuit.ADD(x3, x, 5))

	circuit.Write("circuit.r1cs")
}

cd examples/cubic_equation
go run cubic.go
gnark setup circuit.r1cs
gnark prove circuit.r1cs --pk circuit.pk --input input
gnark verify circuit.proof --vk circuit.vk --input input.public

API vs DSL

While several ZKP projects chose to develop their own language and compiler for the frontend, we designed a high-level API, in plain Go.

Relying on Go ---a mature and widely used language--- and its toolchain, has several benefits.

Developpers can debug, document, test and benchmark their circuits as they would with any other Go program. Circuits can be versionned, unit tested and used into standard continious delivery workflows. IDE integration (we use VSCode) and all these features come for free and are stable accross platforms.

Moreover, gnark is not a black box and exposes APIs like a conventional cryptographic library (think aes.encrypt([]byte)). Complex solutions need this flexibility --- gRPC/REST APIs, serialization protocols, monitoring, logging, ... are all few lines of code away.

Designing your circuit

Caveats

TODO (field overflows, etc)

gnark standard library

Currently gnark provides the following gadgets:

• The Mimc hash function
• Merkle tree (binary, without domain separation)
• Twisted Edwards curve arithmetic (for bn256 and bls381)
• Signature (eddsa aglorithm, following https://tools.ietf.org/html/rfc8032)

Benchmarks

It is difficult to fairly and precisely compare benchmarks between libraries. Some implementations may excel in conditions where others may not (available CPUs, RAM or instruction set, WebAssembly target, ...). Nonetheless, it appears that gnark, is faster than existing state-of-the-art.

Here are our measurements for the Prover, using BLS381 curve. These benchmarks ran on a c5d.metal AWS instance (96 vCPUS, 192GB RAM):

nb constraints	1000	10000	40000	100000	1000000	10000000
bellman (ms/op)	103	183	450	807	5445	60045
gnark (ms/op)	11	67	252	520	4674	56883
gain	-89.3%	-63.4%	-44.0%	-35.6%	-14.2%	-5.3%

On this configuration, for 1M constraints+, we're only using 30% of the CPUs! Work in progress to scale better--- with number of CPUs and number of constraints.

---

Here are some measurements on a consumer laptop (2016 MBP, 8cores, 16GB RAM):

40k constraints	Prove	Verify
bellman (ms/op)	2021	3.69
gnark (ms/op)	1648	3.04
gain	-18.5%	-17.6%

Contributing

Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us. Get in touch: zkteam@consensys.net

Versioning

We use SemVer for versioning. For the versions available, see the tags on this repository.

License

This project is licensed under the Apache 2 License - see the LICENSE file for details