1use ark_ff::PrimeField;
 2use ark_serialize::CanonicalSerialize;
 3use merlin::Transcript as MerlinTranscript;
 4use std::marker::PhantomData;
 5
 6// This Transcript approach is a modified version from https://github.com/arkworks-rs/gemini ,
 7// using Merlin transcript (https://merlin.cool).
 8pub struct Transcript<F: PrimeField> {
 9    phantom: PhantomData<F>,
10    transcript: MerlinTranscript,
11}
12
13impl<F: PrimeField> Transcript<F> {
14    pub fn new() -> Self {
15        Self {
16            phantom: PhantomData::default(),
17            transcript: MerlinTranscript::new(b"transcript"),
18        }
19    }
20    pub fn add<S: CanonicalSerialize>(&mut self, label: &'static [u8], r: &S) {
21        let mut msg = Vec::new();
22        r.serialize_uncompressed(&mut msg).unwrap();
23        self.transcript.append_message(label, &msg);
24    }
25    pub fn get_challenge(&mut self, label: &'static [u8]) -> F {
26        let mut bytes = [0u8; 64];
27        self.transcript.challenge_bytes(label, &mut bytes);
28        let challenge = F::from_le_bytes_mod_order(bytes.as_ref());
29        self.add(b"get challenge", &challenge);
30        challenge
31    }
32    pub fn get_challenge_vec(&mut self, label: &'static [u8], n: usize) -> Vec<F> {
33        let mut c: Vec<F> = vec![F::zero(); n];
34        for i in 0..n {
35            c[i] = self.get_challenge(label);
36        }
37        c
38    }
39}