redjubjub/README.md

A minimal [RedJubjub][redjubjub] implementation for use in [Zebra][zebra].

Two parameterizations of RedJubjub are used in Zcash, one for `BindingSig`
and one for `SpendAuthSig`. This library distinguishes these in the type
system, using the [sealed] `SigType` trait as a type-level enum.

In addition to the usual `Signature`, `SecretKey`, `PublicKey` types, the
library also provides `PublicKeyBytes`, a [refinement] of a `[u8; 32]`
indicating that bytes represent an encoding of a RedJubjub public key. This
allows the `PublicKey` type to cache verification checks related to the
public key encoding.

## Examples

Creating a `BindingSig`, serializing and deserializing it, and verifying the
signature:

```
# use std::convert::TryFrom;
use rand::thread_rng;
use redjubjub::*;

let msg = b"Hello!";

// Generate a secret key and sign the message
let sk = SecretKey::<Binding>::new(thread_rng());
let sig = sk.sign(thread_rng(), msg);

// Types can be converted to raw byte arrays using From/Into
let sig_bytes: [u8; 64] = sig.into();
let pk_bytes: [u8; 32] = PublicKey::from(&sk).into();

// Deserialize and verify the signature.
let sig: Signature<Binding> = sig_bytes.into();
assert!(
    PublicKey::try_from(pk_bytes)
        .and_then(|pk| pk.verify(msg, &sig))
        .is_ok()
);
```

## docs

```shell,no_run
cargo doc --features "nightly" --open
```

[redjubjub]: https://zips.z.cash/protocol/protocol.pdf#concretereddsa
[zebra]: https://github.com/ZcashFoundation/zebra
[refinement]: https://en.wikipedia.org/wiki/Refinement_type
[sealed]: https://rust-lang.github.io/api-guidelines/future-proofing.html#sealed-traits-protect-against-downstream-implementations-c-sealed