Bevis; Fiat-Shamir Without The Hassle

bevis (be- +‎ vis) meaning "proof" in the Scandinavian languages, aims to make implementing public-coin arguments in the Rust substantially easier by eliminating repetitive and error prone implementation details of Fiat-Shamir. Bevis aims to have minimal dependencies (serde and rand_core) and no/very minimal run-time overhead, consisting primarily of a collection of types, traits and procedural macros.

Here is a simplified example of implementing Schnorr using Bevis and curve25519-dalek.

```rust use serde::{Serialize, Deserialize};

[derive(Serialize, Deserialize)]

struct Comm { v: RistrettoPoint, }

[derive(Serialize, Deserialize)]

struct Resp { z: Scalar }

[derive(Serialize, Deserialize)]

struct Pf { a: Msg, z: Resp, }

fn verify(ts: &mut T, pk: &RistrettoPoint, pf: Pf) -> bool { // add the public key ts.append(pk);

// receive first round msg
let a = ts.recv(pf.a);

// get a challenge (transcript impl. RngCore and CryptoRng)
let c = Scalar::random(ts);

// check
c * pk + pf.a == pf.z *

} ```