The GNU Nettle cryptographic library is out with a major new update that introduces support for SLH-DSA, the post-quantum signature scheme selected by NIST for the FIPS 205 standard.

Nettle 4.0 fully supports SLH-DSA signatures for this standard also known as SPHINCS+ algorithm. SLH-DSA is stateless and secure against classic and quantum computing attacks. SLH-DSA can ultimately serve as a replacement to RSA, ECDSA, and similar algorithms.

The Nettle 4.0 release does break some APIs/ABIs for developers to be aware of. Among the ABI changes are introducing 16-byte alignment for some types to help with SIMD load and store instruction performance.