Module slh_dsa 

SLH-DSA: Stateless Hash-Based Digital Signature Standard (FIPS 205).

This crate provides a pure-Rust implementation of SLH-DSA (formerly known as SPHINCS+), a post-quantum digital signature scheme standardized in FIPS 205. SLH-DSA is purely hash-based: its security relies only on the properties of cryptographic hash functions, with no algebraic structure (lattices, codes, etc.) that could be exploited by quantum or classical algorithms beyond generic attacks.

Architecture

SLH-DSA is built from a hierarchy of hash-based primitives:

1. WOTS+ – A one-time signature scheme that signs a single n-byte message using hash chains (see wots).
2. XMSS – An eXtended Merkle Signature Scheme that authenticates 2^h’ WOTS+ keys via a binary Merkle tree, producing a few-time signature (see xmss).
3. Hypertree – A tree of XMSS trees stacked in d layers, giving a many-time signature scheme with a total tree height of h = d * h' (see hypertree).
4. FORS – A Forest of Random Subsets, a few-time signature used to sign the message digest before passing it to the hypertree (see fors).
5. SLH-DSA – The top-level scheme that combines FORS + Hypertree to produce a stateless, many-time signature (see slh).

Supported parameter sets

This crate implements all six SHAKE-based parameter sets defined in FIPS 205 Section 11:

Type	128-bit	192-bit	256-bit
Small (s)	Shake128s	Shake192s	Shake256s
Fast (f)	Shake128f	Shake192f	Shake256f

The “s” variants produce smaller signatures; the “f” variants are faster to sign and verify.

Examples

use quantica::slh_dsa::{SlhDsa, Shake128f, OsRng};

// Generate a key pair
let mut rng = OsRng;
let (secret_key, public_key) = SlhDsa::<Shake128f>::keygen(&mut rng).unwrap();

// Sign a message
let message = b"hello, post-quantum world!";
let signature = SlhDsa::<Shake128f>::sign(message, &secret_key, &mut rng).unwrap();

// Verify the signature
let valid = SlhDsa::<Shake128f>::verify(message, &signature, &public_key).unwrap();
assert!(valid);

Re-exports

pub use params::Params;

pub use params::Shake128f;

pub use params::Shake128s;

pub use params::Shake192f;

pub use params::Shake192s;

pub use params::Shake256f;

pub use params::Shake256s;

pub use rng::CryptoRng;

pub use rng::OsRng;

Modules

address

Address structure used to domain-separate hash calls throughout SLH-DSA. ADRS (Address) structure for SLH-DSA (FIPS 205, Section 4.2).

fors

FORS: Forest of Random Subsets few-time signature scheme. FORS: Forest of Random Subsets (FIPS 205, Algorithms 14-17).

hash

SHAKE-based tweakable hash function wrappers (H_msg, PRF, PRF_msg, T_l, H, F). SHAKE-based tweakable hash function wrappers for SLH-DSA (FIPS 205, Section 11.1).

hypertree

Hypertree: a d-layer tree of XMSS trees for many-time signing. Hypertree: a multi-layer tree-of-XMSS-trees structure (FIPS 205, Algorithms 12-13).

params

SLH-DSA parameter set definitions and the Params trait. SLH-DSA parameter sets (FIPS 205, Section 11).

rng

Minimal cryptographic RNG trait and OS-backed implementation. Minimal cryptographic RNG trait and OS-backed implementation.

sha3

Keccak-f[1600] based SHAKE256 implementation (FIPS 202). SHA-3 / SHAKE high-level wrappers used by SLH-DSA (FIPS 205).

slh

Top-level SLH-DSA key generation, signing, and verification algorithms. Top-level SLH-DSA algorithms (FIPS 205, Algorithms 18-22, 24).

wots

WOTS+ one-time signature scheme based on hash chains. WOTS+ one-time signature scheme (FIPS 205, Algorithms 1, 4-8).

xmss

XMSS: eXtended Merkle Signature Scheme combining WOTS+ with a Merkle tree. XMSS: eXtended Merkle Signature Scheme (FIPS 205, Algorithms 9-11).

Structs

Signature

SLH-DSA signature. Type-tagged with P.

SigningKey

SLH-DSA signing key (secret key, 4 * P::N bytes).

SlhDsa

VerifyingKey

SLH-DSA verifying key (public key, 2 * P::N bytes).

Enums

SlhDsaError

Errors that can occur in SLH-DSA operations.