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//! Hazardous Materials: low-level APIs which can be insecure if misused.
//!
//! The traits in this module are not generally recommended, and should only be
//! used in special cases where they are specifically needed.
//!
//! Using them incorrectly can introduce security vulnerabilities. Please
//! carefully read the documentation before attempting to use them.
use crate::Error;
#[cfg(feature = "rand_core")]
use crate::rand_core::CryptoRngCore;
/// Sign the provided message prehash, returning a digital signature.
pub trait PrehashSigner<S> {
/// Attempt to sign the given message digest, returning a digital signature
/// on success, or an error if something went wrong.
///
/// The `prehash` parameter should be the output of a secure cryptographic
/// hash function.
///
/// This API takes a `prehash` byte slice as there can potentially be many
/// compatible lengths for the message digest for a given concrete signature
/// algorithm.
///
/// Allowed lengths are algorithm-dependent and up to a particular
/// implementation to decide.
fn sign_prehash(&self, prehash: &[u8]) -> Result<S, Error>;
}
/// Sign the provided message prehash using the provided external randomness source, returning a digital signature.
#[cfg(feature = "rand_core")]
pub trait RandomizedPrehashSigner<S> {
/// Attempt to sign the given message digest, returning a digital signature
/// on success, or an error if something went wrong.
///
/// The `prehash` parameter should be the output of a secure cryptographic
/// hash function.
///
/// This API takes a `prehash` byte slice as there can potentially be many
/// compatible lengths for the message digest for a given concrete signature
/// algorithm.
///
/// Allowed lengths are algorithm-dependent and up to a particular
/// implementation to decide.
fn sign_prehash_with_rng(
&self,
rng: &mut impl CryptoRngCore,
prehash: &[u8],
) -> Result<S, Error>;
}
/// Verify the provided message prehash using `Self` (e.g. a public key)
pub trait PrehashVerifier<S> {
/// Use `Self` to verify that the provided signature for a given message
/// `prehash` is authentic.
///
/// The `prehash` parameter should be the output of a secure cryptographic
/// hash function.
///
/// Returns `Error` if it is inauthentic or some other error occurred, or
/// otherwise returns `Ok(())`.
///
/// # ⚠️ Security Warning
///
/// If `prehash` is something other than the output of a cryptographically
/// secure hash function, an attacker can potentially forge signatures by
/// solving a system of linear equations.
fn verify_prehash(&self, prehash: &[u8], signature: &S) -> Result<(), Error>;
}