Paper 2026/125 Original: eprint.iacr.org/2026/125 ↗
StarFortress: Hybrid KEMs with Diffie-Hellman Inlining
Abstract
This short paper formally specifies and analyzes the UG hybrid KEM construction from the IRTF CFRG’s recent draft on hybrid (post-quantum/traditional) KEMs. The UG construction is an optimized hybrid of a Diffie-Hellman (DH)-based KEM in a nominal group and a generic IND-CCA KEM. The main optimization is that the group elements derived in the DH-based KEM are “inlined” in the key derivation, saving unnecessary hashing. We perform two security analyses of the UG construction: one shows UG is IND-CCA even if the generic IND-CCA KEM is broken; the other complementary analysis shows UG is IND-CCA even if the DH assumptions in the nominal group are broken (by, e.g., a cryptographically-relevant quantum computer).
Metadata
- Available format(s)
PDF- Category
- Public-key cryptography
- Publication info
- Preprint.
- History
- 2026-01-30: last updated
- 2026-01-26: published
- Short URL
- https://ia.cr/2026/125
- License
- https://creativecommons.org/licenses/by/4.0/
BibTeX
@misc{cryptoeprint:2026/125,
author = {Deirdre Connolly and Paul Grubbs},
title = {StarFortress: Hybrid KEMs with Diffie-Hellman Inlining},
howpublished = {Cryptology {ePrint} Archive, Paper 2026/125},
year = {2026},
url = {https://eprint.iacr.org/2026/125}
}