Paper 2011/649 Original: eprint.iacr.org/2011/649 ↗
On the Security of NMAC and Its Variants
Abstract
We first propose a general equivalent key recovery attack to a $H^2$-MAC variant NMAC$_1$, which is also provable secure, by applying a generalized birthday attack. Our result shows that NMAC$_1$, even instantiated with a secure Merkle-Damgård hash function, is not secure. We further show that this equivalent key recovery attack to NMAC$_1$ is also applicable to NMAC for recovering the equivalent inner key of NMAC, in a related key setting. We propose and analyze a series of NMAC variants with different secret approaches and key distributions, we find that a variant NMAC-E, with secret envelop approach, can withstand most of the known attacks in this paper. However, all variants including NMAC itself, are vulnerable to on-line birthday attack for verifiable forgery. Hence, the underlying cryptographic hash functions, based on Merkle-Damgård construction, should be re-evaluated seriously.
Metadata
- Available format(s)
PDF- Publication info
- Preprint.
- History
- 2011-12-09: last updated
- 2011-12-09: published
- Short URL
- https://ia.cr/2011/649
- License
- https://creativecommons.org/licenses/by/4.0/
BibTeX
@misc{cryptoeprint:2011/649,
author = {Fanbao Liu and Changxiang Shen and Tao Xie and Dengguo Feng},
title = {On the Security of NMAC and Its Variants},
howpublished = {Cryptology {ePrint} Archive, Paper 2011/649},
year = {2011},
url = {https://eprint.iacr.org/2011/649}
}