plonky2/README.md

# Plonky2 & more

This repository was originally for Plonky2, a SNARK implementation based on techniques from PLONK and FRI. It has since expanded to include tools such as Starky, a highly performant STARK implementation.

## Codex fork

This repo is Codex's fork of [Polygon Zero's Plonky2 repository](https://github.com/0xPolygonZero/plonky2/).

For now at least, our modifications are in the [`codex` branch](https://github.com/codex-storage/plonky2/tree/codex).

These include:

- [x] option to turn off randomizing unused wires
- [x] option to export the witness and related metadata
- [x] simple web-based tool to visualize the witness
- [ ] tooling to analyze circuits
- [ ] detailed documentation of how Plonky2 actually works
- [ ] maybe some additional gates / gadgets
- [ ] support for Poseidon2-Goldilocks hash
- [ ] support for Poseidon2-BN254 hash (for more efficient BN254 wrapper)
- [ ] support for Monolith hash (ideally also for recursion)
- [ ] BN254 wrapper circuit (Groth16 and/or Plonk-KZG)

## Documentation

For more details about the Plonky2 argument system, see this [writeup](plonky2/plonky2.pdf).

Polymer Labs has written up a helpful tutorial [here](https://polymerlabs.medium.com/a-tutorial-on-writing-zk-proofs-with-plonky2-part-i-be5812f6b798)!


## Examples

A good starting point for how to use Plonky2 for simple applications is the included examples:

* [`factorial`](plonky2/examples/factorial.rs): Proving knowledge of 100!
* [`fibonacci`](plonky2/examples/fibonacci.rs): Proving knowledge of the hundredth Fibonacci number
* [`range_check`](plonky2/examples/range_check.rs): Proving that a field element is in a given range
* [`square_root`](plonky2/examples/square_root.rs): Proving knowledge of the square root of a given field element
* [`lookup`](plonky2/examples/lookup_example.rs): Proving that a few members of an arithmetic progression are all primes

To run an example, use

```sh
cargo run --example <example_name>
```


## Building

Plonky2 requires a recent nightly toolchain, although we plan to transition to stable in the future.

To use a nightly toolchain for Plonky2 by default, you can run
```
rustup override set nightly
```
in the Plonky2 directory.


## Running

To see recursion performance, one can run this bench, which generates a chain of three recursion proofs:

```sh
RUSTFLAGS=-Ctarget-cpu=native cargo run --release --example bench_recursion -- -vv
```

## Jemalloc

Plonky2 prefers the [Jemalloc](http://jemalloc.net) memory allocator due to its superior performance. To use it, include `jemallocator = "0.5.0"` in your `Cargo.toml` and add the following lines
to your `main.rs`:

```rust
use jemallocator::Jemalloc;

#[global_allocator]
static GLOBAL: Jemalloc = Jemalloc;
```

Jemalloc is known to cause crashes when a binary compiled for x86 is run on an Apple silicon-based Mac under [Rosetta 2](https://support.apple.com/en-us/HT211861). If you are experiencing crashes on your Apple silicon Mac, run `rustc --print target-libdir`. The output should contain `aarch64-apple-darwin`. If the output contains `x86_64-apple-darwin`, then you are running the Rust toolchain for x86; we recommend switching to the native ARM version.

## Documentation

Generate documentation locally:

```sh
cargo doc --no-deps --open
```

## Contributing guidelines

See [CONTRIBUTING.md](./CONTRIBUTING.md).

## Licenses

All crates of this monorepo are licensed under either of

* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
* MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)

at your option.


## Security

This code has not yet been audited, and should not be used in any production systems.

While Plonky2 is configurable, its defaults generally target 100 bits of security. The default FRI configuration targets 100 bits of *conjectured* security based on the conjecture in [ethSTARK](https://eprint.iacr.org/2021/582).

Plonky2's default hash function is Poseidon, configured with 8 full rounds, 22 partial rounds, a width of 12 field elements (each ~64 bits), and an S-box of `x^7`. [BBLP22](https://tosc.iacr.org/index.php/ToSC/article/view/9850) suggests that this configuration may have around 95 bits of security, falling a bit short of our 100 bit target.


## Links

#### Actively maintained

- [Polygon Zero's zkEVM](https://github.com/0xPolygonZero/zk_evm), an efficient Type 1 zkEVM built on top of Starky and plonky2

#### No longer maintained

- [System Zero](https://github.com/0xPolygonZero/system-zero), a zkVM built on top of Starky
- [Waksman](https://github.com/0xPolygonZero/plonky2-waksman), Plonky2 gadgets for permutation checking using Waksman networks
- [Insertion](https://github.com/0xPolygonZero/plonky2-insertion), Plonky2 gadgets for insertion into a list
- [u32](https://github.com/0xPolygonZero/plonky2-u32), Plonky2 gadgets for u32 arithmetic
- [ECDSA](https://github.com/0xPolygonZero/plonky2-ecdsa), Plonky2 gadgets for the ECDSA algorithm