## Cryptology ePrint Archive: Report 2012/018

Attacks and Security Proofs of EAX-Prime

Kazuhiko Minematsu and Stefan Lucks and Hiraku Morita and Tetsu Iwata

Abstract: EAX$'$ (EAX-prime) is an authenticated encryption (AE) specified by ANSI C12.22 as a standard security function for Smart Grid. EAX$'$ is based on EAX proposed by Bellare, Rogaway, and Wagner. While EAX has a proof of security based on the pseudorandomness of the internal blockcipher, no published security result is known for EAX$'$.

This paper studies the security of EAX$'$ and shows that there is a sharp distinction in security of EAX$'$ depending on the input length. EAX$'$ encryption takes two inputs, called cleartext and plaintext, and we present various efficient attacks against EAX$'$ using single-block cleartext and plaintext. At the same time we prove that if cleartexts are always longer than one block, it is provably secure based on the pseudorandomness of the blockcipher.

Category / Keywords: Authenticated Encryption, EAX, EAX$'$, Attack, Provable Security

Date: received 11 Jan 2012, last revised 13 May 2013

Contact author: k-minematsu at ah jp nec com

Available format(s): PDF | BibTeX Citation

Note: The previous title was "Cryptanalysis of EAXprime". A part of the result was presented at DIAC, and a preliminary version of this paper appears in the proceedings of FSE 2013. This is the full version.

Short URL: ia.cr/2012/018

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