Cryptology ePrint Archive: Report 2015/918

Finding State Collisions in the Authenticated Encryption Stream Cipher ACORN

Md Iftekhar Salam and Kenneth Koon-Ho Wong and Harry Bartlett and Leonie Simpson and Ed Dawson and Josef Pieprzyk

Abstract: This paper analyzes the authenticated encryption algorithm ACORN, a candidate in the CAESAR cryptographic competition. We identify weaknesses in the state update function of ACORN which result in collisions in the internal state of ACORN. This paper shows that for a given set of key and initialization vector values we can construct two distinct input messages which result in a collision in the ACORN internal state. Using a standard PC the collision can be found almost instantly when the secret key is known.

Category / Keywords: secret-key cryptography / CAESAR, Authenticated encryption, AEAD, ACORN, collision, stream cipher, integrity, symmetric encryption, message authentication code

Date: received 21 Sep 2015

Contact author: m salam at qut edu au

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Version: 20150922:210023 (All versions of this report)

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