Cryptology ePrint Archive: Report 2015/407

Higher-Order Cryptanalysis of LowMC

Christoph Dobraunig and Maria Eichlseder and Florian Mendel

Abstract: LowMC is a family of block ciphers developed particularly for use in multi-party computations and fully homomorphic encryption schemes, where the main performance penalty comes from non-linear operations. Thus, LowMC has been designed to minimize the total quantity of logical "and" operations, as well as the "and" depth. To achieve this, the LowMC designers opted for an incomplete S-box layer that does not cover the complete state, and compensate for it with a very dense, randomly chosen linear layer. In this work, we exploit this design strategy in a cube-like key-recovery attack. We are able to recover the secret key of a round-reduced variant of LowMC with 80-bit security, where the number of rounds is reduced from 11 to 9. Our attacks are independent of the actual instances of the used linear layers and therefore, do not exploit possible weak choices of them. From our results, we conclude that the resulting security margin of 2 rounds is smaller than expected.

Category / Keywords: secret-key cryptography / cryptanalysis, higher-order cryptanalysis, LowMC, key recovery, zero-sum distinguisher

Original Publication (in the same form): ICISC 2015
DOI:
10.1007/978-3-319-30840-1_6

Date: received 29 Apr 2015, last revised 25 Aug 2016

Contact author: maria eichlseder at iaik tugraz at

Available format(s): PDF | BibTeX Citation

Note: updated publication information (ICISC 2015)

Version: 20160825:133831 (All versions of this report)

Short URL: ia.cr/2015/407

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