### On the security margin of MAC striping

Thomas Eisenbarth, Aaron Meyerowitz, and Rainer Steinwandt

##### Abstract

MAC striping has been suggested as a technique to authenticate encrypted payloads using short tags. For an idealized MAC scheme, the probability of a selective forgery has been estimated as $\binom{\ell+m}{m}^{-1}\cdot 2^{-m}$, when utilizing MAC striping with $\ell$-bit payloads and $m$-bit tags. We show that this estimate is too optimistic. For $m\le\ell$ and any payload, we achieve a selective forgery with probability $\ge \binom{\ell+m}{m}^{-1}$, and usually many orders of magnitude more than that.

Available format(s)
Category
Secret-key cryptography
Publication info
Preprint. MINOR revision.
Keywords
cryptanalysisMACMAC stripingselective forgery
Contact author(s)
teisenbarth @ wpi edu
meyerowi @ fau edu
rsteinwa @ fau edu
History
Short URL
https://ia.cr/2015/089

CC BY

BibTeX

@misc{cryptoeprint:2015/089,
author = {Thomas Eisenbarth and Aaron Meyerowitz and Rainer Steinwandt},
title = {On the security margin of MAC striping},
howpublished = {Cryptology ePrint Archive, Paper 2015/089},
year = {2015},
note = {\url{https://eprint.iacr.org/2015/089}},
url = {https://eprint.iacr.org/2015/089}
}

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