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use alloc::vec::Vec;
use core::fmt;
use crate::{
Decoding, DuplexSpongeInterface, Encoding, NargDeserialize, StdHash, VerificationError,
VerificationResult,
};
/// [`VerifierState`] is the verifier state.
///
/// ```
/// use spongefish::{StdHash, VerifierState};
///
/// let verifier = VerifierState::from_parts(StdHash::default(), b"extra bytes");
/// assert!(verifier.check_eof().is_err());
///
/// let verifier = VerifierState::from_parts(StdHash::default(), b"");
/// assert!(verifier.check_eof().is_ok());
/// ```
pub struct VerifierState<'a, H = StdHash>
where
H: DuplexSpongeInterface,
{
/// The public coins for the protocol.
#[cfg(feature = "yolocrypto")]
pub duplex_sponge_state: H,
#[cfg(not(feature = "yolocrypto"))]
pub(crate) duplex_sponge_state: H,
/// The NARG string currently read.
pub(crate) narg_string: &'a [u8],
}
impl<H: DuplexSpongeInterface> VerifierState<'_, H> {
/// Reads a prover message and absorbs it into the duplex sponge state.
pub fn prover_message<T: Encoding<[H::U]> + NargDeserialize>(
&mut self,
) -> VerificationResult<T> {
let mut narg_string = self.narg_string;
let message = T::deserialize_from_narg(&mut narg_string)?;
self.duplex_sponge_state.absorb(message.encode().as_ref());
self.narg_string = narg_string;
Ok(message)
}
/// Absorbs a public message without consuming the transcript.
///
/// ```
/// let proof = [0u8; 0];
/// let mut verifier = spongefish::domain_separator!("examples";"VerifierState::public_message")
/// .instance(&0u32)
/// .std_verifier(&proof);
/// verifier.public_message(&123u32);
/// assert!(verifier.check_eof().is_ok());
/// ```
pub fn public_message<T: Encoding<[H::U]> + ?Sized>(&mut self, message: &T) {
self.duplex_sponge_state.absorb(message.encode().as_ref());
}
/// Returns a verifier message `T` that is uniformly distributed and implements `Encoding<[H::U]>`.
pub fn verifier_message<T: Decoding<[H::U]>>(&mut self) -> T {
let mut buf = T::Repr::default();
self.duplex_sponge_state.squeeze(buf.as_mut());
T::decode(buf)
}
/// Absorbs a slice of public messages.
///
/// ```
/// let mut verifier = spongefish::domain_separator!("examples"; "VerifierState::public_messages")
/// .instance(&0u32)
/// .std_verifier(&[]);
/// verifier.public_messages(&[1u32, 2u32]);
/// assert!(verifier.check_eof().is_ok());
/// ```
pub fn public_messages<T: Encoding<[H::U]>>(&mut self, messages: &[T]) {
for message in messages {
self.public_message(message);
}
}
/// Absorbs an iterator of public messages.
///
/// ```
/// let mut verifier = spongefish::domain_separator!("examples"; "VerifierState::public_messages_iter")
/// .instance(&0u32)
/// .std_verifier(&[]);
/// verifier.public_messages_iter([1u32, 2u32]);
/// assert!(verifier.check_eof().is_ok());
/// ```
pub fn public_messages_iter<J>(&mut self, messages: J)
where
J: IntoIterator,
J::Item: Encoding<[H::U]>,
{
messages
.into_iter()
.for_each(|message| self.public_message(&message));
}
/// Reads a fixed-size array of prover messages `T`, each implementing `Encoding<[H::U]>`.
pub fn prover_messages<T: Encoding<[H::U]> + NargDeserialize, const N: usize>(
&mut self,
) -> VerificationResult<[T; N]> {
let result = self.prover_messages_vec::<T>(N)?;
Ok(result.try_into().unwrap_or_else(|_| unreachable!()))
}
/// Reads `len` prover messages `T` into a vector, each implementing `Encoding<[H::U]>`.
pub fn prover_messages_vec<T: Encoding<[H::U]> + NargDeserialize>(
&mut self,
len: usize,
) -> VerificationResult<Vec<T>> {
(0..len).map(|_| self.prover_message()).collect()
}
/// Returns `Ok(())` if the transcript has been fully consumed, otherwise a `VerificationError`.
pub fn check_eof(self) -> VerificationResult<()> {
if self.narg_string.is_empty() {
Ok(())
} else {
Err(VerificationError)
}
}
}
impl<H> fmt::Debug for VerifierState<'_, H>
where
H: DuplexSpongeInterface,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "VerifierState<{}>", core::any::type_name::<H>())
}
}
impl<'a> VerifierState<'a, StdHash> {
#[cfg(feature = "sha3")]
/// Builds a verifier using the default sponge implementation.
#[must_use]
pub fn default_std(narg_string: &'a [u8]) -> Self {
VerifierState {
duplex_sponge_state: StdHash::default(),
narg_string,
}
}
}
impl<'a, H: DuplexSpongeInterface> VerifierState<'a, H> {
/// Creates a verifier state from a duplex sponge and transcript slice.
pub const fn from_parts(duplex_sponge_state: H, narg_string: &'a [u8]) -> Self {
VerifierState {
duplex_sponge_state,
narg_string,
}
}
}
impl<'a, H> VerifierState<'a, H>
where
H: DuplexSpongeInterface<U = u8> + Default,
{
/// Initializes a verifier state from protocol and session identifiers plus a transcript.
#[must_use]
pub fn new(protocol_id: &[u8; 64], session_id: &[u8; 64], narg_string: &'a [u8]) -> Self {
let mut verifier_state = VerifierState {
duplex_sponge_state: H::default(),
narg_string,
};
verifier_state.public_message(protocol_id);
verifier_state.public_message(session_id);
verifier_state
}
}
impl<'a> VerifierState<'a, StdHash> {
#[cfg(feature = "sha3")]
/// Initializes a verifier with `StdHash` as duplex sponge.
#[must_use]
pub fn new_std(protocol_id: &[u8; 64], session_id: &[u8; 64], narg_string: &'a [u8]) -> Self {
let mut verifier_state = VerifierState {
duplex_sponge_state: StdHash::from_protocol_id(*protocol_id),
narg_string,
};
verifier_state.public_message(session_id);
verifier_state
}
}