## Cryptology ePrint Archive: Report 2019/1352

Spectral analysis of ZUC-256

Jing Yang and Thomas Johansson and Alexander Maximov

Abstract: In this paper we develop a number of generic techniques and algorithms in spectral analysis of large linear approximations for use in cryptanalysis. We apply the developed tools for cryptanalysis of ZUC-256 and give a distinguishing attack with complexity around $2^{236}$. Although the attack is only $2^{20}$ times faster than exhaustive key search, the result indicates that ZUC-256 does not provide a source with full 256-bit entropy in the generated keystream, which would be expected from a 256-bit key. To the best of our knowledge, this is the first known academic attack on full ZUC-256 with a computational complexity that is below exhaustive key search.

Category / Keywords: secret-key cryptography / ZUC-256, Stream Cipher, 5G Mobile System Security

Original Publication (in the same form): IACR-FSE-2020

Date: received 23 Nov 2019, last revised 19 Feb 2020

Contact author: alexander maximov at ericsson com

Available format(s): PDF | BibTeX Citation

Short URL: ia.cr/2019/1352

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