## Cryptology ePrint Archive: Report 2012/544

Differential Analysis of the LED Block Cipher

Florian Mendel and Vincent Rijmen and Deniz Toz and Kerem Varici

Abstract: In this paper, we present a security analysis of the lightweight block cipher LED proposed by Guo et al. at CHES 2011. Since the design of LED is very similar to the Even-Mansour scheme, we first review existing attacks on this scheme and extend them to related-key and related-key-cipher settings before we apply them to LED. We obtain results for $12$ and $16$ rounds (out of $32$) for LED-$64$ and $16$ and $24$ rounds (out of $48$) for LED-$128$. Furthermore, we present an observation on full LED in the related-key-cipher setting. For all these attacks we need to find good differentials for one step (4 rounds) of LED. Therefore, we extend the study of plateau characteristics for AES-like structures from two rounds to four rounds when the key addition is replaced with a constant addition. We introduce an algorithm that can be used to find good differentials and right pairs for one step of LED. To be more precise, we can find more than $2^{10}$ right pairs for one step of LED with complexity of $2^{16}$ and memory requirement of $5 \times 2^{17}$. Moreover, a similar algorithm can also be used to find iterative characteristics for LED.

Category / Keywords: secret-key cryptography / Block ciphers, Even-Mansour construction, Plateau characteristics, cryptanalysis

Publication Info: this is the full version of the Asiacrpyt 2012 paper

Date: received 17 Sep 2012, last revised 22 Nov 2012

Contact author: kerem varici at esat kuleuven be

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