Paper 2023/1808
Small Stretch Problem of the DCT Scheme and How to Fix It
Abstract
DCT is a beyond-birthday-bound~(BBB) deterministic authenticated encryption~(DAE) mode proposed by Forler et al. in ACISP 2016, ensuring integrity by redundancy. The instantiation of DCT employs the BRW polynomial, which is more efficient than the usual polynomial in GCM by reducing half of the multiplication operations. However, we show that DCT suffers from a small stretch problem similar to GCM. When the stretch length $\tau$ is small, choosing a special $m$-block message, we can reduce the number of queries required by a successful forgery to $\mathcal{O}(2^{\tau}/m)$. We emphasize that this attack efficiently balances space and time complexity but does not contradict the security bounds of DCT. Finally, we propose an improved scheme named Robust DCT~(RDCT) with a minor change to DCT, which improves the security when $\tau$ is small and makes it resist the above attack.
Metadata
- Available format(s)
-
PDF
- Category
- Secret-key cryptography
- Publication info
- Published by the IACR in TOSC 2024
- Keywords
- DCTDeterministic Authenticated EncryptionAEADBRW polynomialForgery AttackStretch
- Contact author(s)
-
chenyuchao @ mail sdu edu cn
guotingting4633 @ gmail com
hulei @ iie ac cn
sln-8108 @ 163 com
maoshuping @ iie ac cn
w rocking @ gmail com - History
- 2024-04-13: last of 3 revisions
- 2023-11-23: received
- See all versions
- Short URL
- https://ia.cr/2023/1808
- License
-
CC BY
BibTeX
@misc{cryptoeprint:2023/1808,
author = {Yuchao Chen and Tingting Guo and Lei Hu and Lina Shang and Shuping Mao and Peng Wang},
title = {Small Stretch Problem of the {DCT} Scheme and How to Fix It},
howpublished = {Cryptology {ePrint} Archive, Paper 2023/1808},
year = {2023},
url = {https://eprint.iacr.org/2023/1808}
}