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use crate::{
errors::{self, MuSigError, SchnorrError},
BatchVerification, MuSigContext, Multimessage, PublicKey, Signature, SingleVerifier,
};
use bacteria::Transcript;
use mohan::dalek::{constants::RISTRETTO_BASEPOINT_POINT, scalar::Scalar};
use std::borrow::Borrow;
use std::iter;
pub trait Multisignature {
fn sign_multi<P, M>(
privkeys: P,
messages: Vec<(PublicKey, M)>,
transcript: &mut Transcript,
) -> Result<Signature, SchnorrError>
where
M: AsRef<[u8]>,
P: IntoIterator,
P::Item: Borrow<Scalar>,
P::IntoIter: ExactSizeIterator;
fn verify_multi<M: AsRef<[u8]>>(
&self,
transcript: &mut Transcript,
messages: Vec<(PublicKey, M)>,
) -> Result<(), SchnorrError>;
fn verify_multi_batched<M: AsRef<[u8]>>(
&self,
transcript: &mut Transcript,
messages: Vec<(PublicKey, M)>,
batch: &mut impl BatchVerification,
);
}
impl Multisignature for Signature {
fn sign_multi<P, M>(
privkeys: P,
messages: Vec<(PublicKey, M)>,
transcript: &mut Transcript,
) -> Result<Signature, SchnorrError>
where
M: AsRef<[u8]>,
P: IntoIterator,
P::Item: Borrow<Scalar>,
P::IntoIter: ExactSizeIterator,
{
let mut privkeys = privkeys.into_iter().peekable();
if messages.len() != privkeys.len() {
return Err(errors::from_musig(MuSigError::BadArguments));
}
if privkeys.len() == 0 {
return Err(errors::from_musig(MuSigError::BadArguments));
}
let context = Multimessage::new(messages);
let mut rng = transcript
.build_rng()
.rekey_with_witness_bytes(b"x_i", privkeys.peek().unwrap().borrow().as_bytes())
.finalize(&mut rand::thread_rng());
let r = Scalar::random(&mut rng);
let R = (RISTRETTO_BASEPOINT_POINT * r).compress();
context.commit(transcript);
transcript.commit_point(b"R", &R);
let mut s = r;
for (i, x_i) in privkeys.enumerate() {
let mut t = transcript.clone();
let c_i = context.challenge(i, &mut t);
s = s + c_i * x_i.borrow();
}
Ok(Signature { s, R })
}
fn verify_multi<M: AsRef<[u8]>>(
&self,
transcript: &mut Transcript,
messages: Vec<(PublicKey, M)>,
) -> Result<(), SchnorrError> {
SingleVerifier::verify(|verifier| self.verify_multi_batched(transcript, messages, verifier))
}
fn verify_multi_batched<M: AsRef<[u8]>>(
&self,
transcript: &mut Transcript,
messages: Vec<(PublicKey, M)>,
batch: &mut impl BatchVerification,
) {
let context = Multimessage::new(messages);
context.commit(transcript);
transcript.commit_point(b"R", &self.R);
let n = context.len();
batch.append(
-self.s,
iter::once(Scalar::one())
.chain((0..n).map(|i| context.challenge(i, &mut transcript.clone()))),
iter::once(self.R.decompress())
.chain((0..n).map(|i| Some(context.key(i).into_point()))),
);
}
}