quantica/ml_dsa/
rng.rs

1// SPDX-License-Identifier: Apache-2.0
2// Copyright 2026 Cédric Mesnil <cslashm@pm.me>
3
4//! Minimal cryptographic RNG trait and OS-backed implementation.
5//!
6//! Provides the [`CryptoRng`] trait used by ML-DSA for key generation and
7//! hedged signing, along with [`OsRng`], a simple implementation backed by
8//! the operating system's entropy source.
9
10use super::MlDsaError;
11
12/// Trait for cryptographic random byte generation.
13///
14/// Implementors must fill the destination buffer with cryptographically
15/// secure random bytes. This trait is used as a trait object (`&mut dyn CryptoRng`)
16/// throughout the ML-DSA API to allow callers to supply their own RNG.
17pub trait CryptoRng {
18    /// Fill `dest` with cryptographically secure random bytes.
19    ///
20    /// # Errors
21    ///
22    /// Returns [`MlDsaError::RngFailure`] if the underlying entropy source
23    /// is unavailable or fails.
24    fn fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), MlDsaError>;
25}
26
27/// OS-backed cryptographic RNG reading from `/dev/urandom`.
28///
29/// Only available with the `std` feature. In `no_std` builds, callers
30/// must supply their own [`CryptoRng`] implementation.
31#[cfg(feature = "std")]
32pub struct OsRng;
33
34#[cfg(feature = "std")]
35impl CryptoRng for OsRng {
36    fn fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), MlDsaError> {
37        use std::io::Read;
38        let mut f = std::fs::File::open("/dev/urandom").map_err(|_| MlDsaError::RngFailure)?;
39        f.read_exact(dest).map_err(|_| MlDsaError::RngFailure)
40    }
41}
quantica/ml_dsa/rng.rs

quantica/ml_dsa/
rng.rs
