SLH-DSA

0.2.2 verified Fri May 01 auth: no python

Pure Python implementation of the SLH-DSA (Stateless Hash-Based Digital Signature Algorithm) based on FIPS 205. Version 0.2.2 includes fixes for digest lengths and supports key import/export in PKCS format, signing, and verification. Actively maintained.

pip install slh-dsa

Common errors

error ModuleNotFoundError: No module named 'slh_dsa' ↓

cause Package not installed or import name mismatch (the package uses underscore in the module name, not hyphen).

fix

Install with pip install slh-dsa and import as from slh_dsa import SLHDSA.

error AttributeError: 'SLHDSA' object has no attribute 'sign' ↓

cause Old version (<0.2.1) may lack the sign method; using wrong object instance.

fix

Upgrade to latest version: pip install --upgrade slh-dsa. Use SLHDSA.new('shake_128') to create a private key object.

Warnings

gotcha The library uses 'shake_128', 'shake_256', 'sha2_192', 'sha2_256' as algorithm identifiers. Ensure you use the exact string matching the intended security level. ↓

fix Use one of: 'shake_128', 'shake_256', 'sha2_192', 'sha2_256'. Check FIPS 205 for parameter sets.

gotcha Signing with a private key does not return a serializable format; you must export the key via `export_pkcs()` before sending or storage. The private key object is not directly serializable. ↓

fix Use `private_key.export_pkcs()` to get a bytes representation, and `SLHDSA.import_pkcs(data)` to reload.

breaking Version 0.2.0 introduced mypyc compilation, which may cause import failures on some platforms (e.g., Alpine Linux, ARM32). The package may not be precompiled for all architectures. ↓

fix If import fails with 'ModuleNotFoundError' or 'ImportError: cannot import name', consider installing from source with `pip install slh-dsa --no-binary slh-dsa`.

Imports

SLHDSA
```
from slh_dsa import SLHDSA
```
Standard import path.

Quickstart

Generate SLH-DSA keys, sign, and verify.

from slh_dsa import SLHDSA

# Generate a private key (SLH-DSA with SHAKE-128, security level 1)
private_key = SLHDSA.new('shake_128')
message = b"Hello, world!"
signature = private_key.sign(message)

# Extract public key (serialized PKCS format)
public_key_pem = private_key.public_key().export_pkcs()

# Verify signature
from slh_dsa import verify
verify(public_key_pem, message, signature)  # Returns True/False