Cryptology ePrint Archive: Report 2018/048

Impossible Differential Cryptanalysis on Deoxys-BC-256

Alireza mehrdad and Farokhlagha Moazami and Hadi Soleimany

Abstract: Deoxys is a third-round candidate of the CAESAR competition. This paper presents the first impossible differential cryptanalysis of Deoxys-BC-256 which is used in Deoxys as an internal tweakable block cipher. First, we find a 4.5-round ID characteristic by utilizing a miss-in-the-middle-approach. We then present several cryptanalyses based upon the 4.5 rounds distinguisher against round-reduced Deoxys-BC-256 in both single-key and related-key settings. Our contributions include impossible differential attacks on up to 8-rounds Deoxys-BC-256 in the tweak-key model which is, to the best of our knowledge, the first independent investigation of the security of Deoxys-BC-256 in the single-key model. Our attack reaches 9 rounds in the related-key related-tweak model which has a slightly higher data complexity than the best previous results obtained by a rectangle attack presented at FSE 2018 but requires a lower memory complexity with an equal time complexity.

Category / Keywords: secret-key cryptography / authenticated encryption, block cipher, Deoxys-BC, related- tweak, related-key, impossible differential cryptanalysis.

Date: received 9 Jan 2018

Contact author: a mehrdad at mail sbu ac ir

Available format(s): PDF | BibTeX Citation

Version: 20180115:002812 (All versions of this report)

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