Erlang/OTP and Bouncy Castle now supporting SLH-DSA in end-entity certificates

[John Mattsson]

Hi,

We constantly try to maintain an overview of what different libraries support, especially now that we are in the middle of the PQC migration.

While several TLS libraries have supported SLH-DSA in CA certificates for some time, I’m happy to report that both Erlang/OTP [1] and Bouncy Castle now support SLH-DSA as the public key in end-entity certificates. They also support ML-DSA and ML-KEM. SLH-DSA performance is adequate for all of our telecom use cases. Have I missed any other TLS libraries with comparable support?

Given the risk of potential future attacks against lattice-based schemes such as the one discussed in [2], I believe all libraries should also support SLH-DSA and HQC-KEM. Note that PQ/T hybrids do not help at all.

Cheers,

John Preuß Mattsson

[1] https://www.erlang.org/

[2] https://eprint.iacr.org/2026/1591