# vrf-rs
[](https://crates.io/crates/vrf) [](https://docs.rs/vrf) [](https://github.com/witnet/vrf-rs/actions/workflows/rust.yml)
`vrf-rs` is an open source implementation of Verifiable Random Functions (VRFs) written in Rust.
_DISCLAIMER: This is experimental software. Be careful!_
The library can be built using `cargo` and the examples can be executed with:
```bash
cargo build
cargo run --example <example_name>
```
## Elliptic Curve VRF
This module uses the OpenSSL library to offer Elliptic Curve Verifiable Random Function (VRF) functionality.
It follows the algorithms described in:
* [VRF-draft-05](https://tools.ietf.org/pdf/draft-irtf-cfrg-vrf-05)
* [RFC6979](https://tools.ietf.org/html/rfc6979)
Currently the supported cipher suites are:
* `P256_SHA256_TAI`: the aforementioned algorithms with `SHA256` and the `secp256r1` curve (aka `NIST P-256`).
* `K163_SHA256_TAI`: the aforementioned algorithms with `SHA256` and the `sect163k1` curve (aka `NIST K-163`).
* `SECP256K1_SHA256_TAI`: the aforementioned algorithms with `SHA256` and the `secp256k1` curve.
### Example
Create and verify a VRF proof by using the cipher suite `SECP256K1_SHA256_TAI`:
```rust
use {vrf::openssl::{CipherSuite, ECVRF}, VRF};
fn main() {
// Initialization of VRF context by providing a curve
let mut vrf = ECVRF::from_suite(CipherSuite::SECP256K1_SHA256_TAI).unwrap();
// Inputs: Secret Key, Public Key (derived) & Message
let secret_key =
hex::decode("c9afa9d845ba75166b5c215767b1d6934e50c3db36e89b127b8a622b120f6721").unwrap();
let public_key = vrf.derive_public_key(&secret_key).unwrap();
let message: &[u8] = b"sample";
// VRF proof and hash output
let pi = vrf.prove(&secret_key, &message).unwrap();
let hash = vrf.proof_to_hash(&pi).unwrap();
// VRF proof verification (returns VRF hash output)
let beta = vrf.verify(&public_key, &pi, &message);
}
```
A complete example can be found in [examples/basic.rs](https://github.com/witnet/vrf-rs/blob/master/examples/basic.rs). It can be executed with:
```bash
cargo run --example basic
```
## Adding unsupported cipher suites
This library defines a `VRF` trait which can be extended in order to use different curves and algorithms.
```rust
pub trait VRF<PublicKey, SecretKey> {
type Error;
fn prove(&mut self, x: SecretKey, alpha: &[u8]) -> Result<Vec<u8>, Self::Error>;
fn verify(&mut self, y: PublicKey, pi: &[u8], alpha: &[u8]) -> Result<Vec<u8>, Self::Error>;
}
```
## License
`vrf-rs` is published under the [MIT license][license].
[license]: https://github.com/witnet/vrf-rs/blob/master/LICENSE