SLH-DSA (Stateless Hash-Based Digital Signature Algorithm (FIPS 205))

Also known as: SPHINCS+

SLH-DSA is the NIST stateless hash-based signature standard (FIPS 205, August 2024), formerly SPHINCS+. Its security relies only on the hash function, offering a conservative fallback if lattice assumptions are broken. Signatures are large (~8-50 KB) and slow, so SLH-DSA is typically reserved for root/anchor keys and firmware signing rather than online telecom signaling.

Categories: Security ControlsProtocols and StandardsInternet and Routing

SLH-DSA in context

Security controls in telecom span signaling firewalls (SS7/Diameter/GTP screening at the network edge), transport encryption (IPsec, TLS, PRINS), identity and access on OSS/BSS, and monitoring at both the packet and log level. Controls are audited against GSMA FS.11/FS.19/FS.20/FS.36 and, in Europe, NIS2 sectoral rules.

Telecom security is written into standards from 3GPP, GSMA, ETSI, IETF and ITU-T. Understanding which body owns which specification, and how the specs interlock (for example 3GPP TS 33.501 with GSMA FS.34 for 5G SBA security), is essential for both design and audit work.

To place SLH-DSA in the wider telecom-security picture, review ML-DSA, SIRT, Suricata, HMAC-SHA256, Digital Signature and SHA.

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