Cryptology ePrint Archive: Report 2018/332

Differential Cryptanalysis of Round-Reduced Sparx-64/128

Ralph Ankele and Eik List

Abstract: Sparx is a family of ARX-based block ciphers designed according to the long-trail strategy (LTS) that were both introduced by Dinu et al. at ASIACRYPT'16. Similar to the wide-trail strategy, the LTS allows provable upper bounds on the length of differential characteristics and linear paths. Thus, the cipher is a highly interesting target for third-party cryptanalysis. However, the only third-party cryptanalysis on Sparx-64/128 to date was given by Abdelkhalek et al. at AFRICACRYPT'17 who proposed impossible-differential attacks on 15 and 16 (out of 24) rounds.

In this paper, we present chosen-ciphertext differential attacks on 16 rounds of Sparx-64/128. First, we show a truncated-differential analysis that requires $2^{32}$ chosen ciphertexts and approximately $2^{93}$ encryptions. Second, we illustrate the effectiveness of boomerangs on Sparx by a rectangle attack that requires approximately $2^{59.6}$ chosen ciphertexts and about $2^{122.2}$ encryption equivalents. Finally, we also considered a yoyo attack on 16 rounds that, however, requires the full codebook and approximately $2^{126}$ encryption equivalents.

Category / Keywords: Symmetric-key cryptography; cryptanalysis; boomerang; truncated differential; yoyo; ARX

Original Publication (with major differences): ACNS 2018 Applied Cryptography & Network security

Date: received 9 Apr 2018, last revised 10 Apr 2018

Contact author: ralph ankele 2015 at live rhul ac uk

Available format(s): PDF | BibTeX Citation

Note: Fix non-math latex command in abstract

Version: 20180410:153514 (All versions of this report)

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