IACR News item: 14 August 2015
Chrysanthi Mavromati
ePrint Report
Chaskey is a Message Authentication Code (MAC) for 32-bit microcontrollers proposed by Mouha et. al at SAC 2014. Its underlying blockcipher uses an Even-Mansour construction with a permutation
based on the ARX methodology. In this paper, we present key-recovery
attacks against Chaskey in the single and multi-user setting. These attacks are based on recent work by Fouque, Joux and Mavromati presented at Asiacrypt 2014 on Even-Mansour based constructions. We first
show a simple attack on the classical single-user setting which confirms
the security properties of Chaskey. Then, we describe an attack in the
multi-user setting and we recover all keys of 2^{43} users by doing 2^{43} queries
per user. Finally, we show a variant of this attack where we are able to
recover keys of two users in a smaller group of 2^{32} users.
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