Paper 2026/1150 Original: eprint.iacr.org/2026/1150 ↗
The Key Control Security of KDF Combiners
Abstract
At CRYPTO 2025, Bhaumik et al. formalised the notion of Key Control (KC) security of Key Derivation Functions (KDFs). A KC adversary, on seeing the root key of a KDF, attempts to manipulate its auxiliary inputs (the `Context' string) to obtain a derived key from a pre-selected set of keys. In this paper we extend the notion of KC security to Key Combining Functions, which are KDFs that convert two root keys to a single derived key; we name the new notion Combining Key Control (CKC) security. We then investigate the CKC security of KDF Combiners and show that (up to certain limitations) it follows from the KC security of either of the component KDFs.
Metadata
- Available format(s)
PDF- Category
- Cryptographic protocols
- Publication info
- Preprint.
- History
- 2026-06-29: last updated
- 2026-06-03: published
- Short URL
- https://ia.cr/2026/1150
- License
- https://creativecommons.org/licenses/by-nc-sa/4.0/
BibTeX
@misc{cryptoeprint:2026/1150,
author = {Ritam Bhaumik},
title = {The Key Control Security of KDF Combiners},
howpublished = {Cryptology {ePrint} Archive, Paper 2026/1150},
year = {2026},
url = {https://eprint.iacr.org/2026/1150}
}