Generalized Meet in the Middle Cryptanalysis of Block Ciphers With an Automated Search Algorithm

Siavash Ahmadi,Mohammad Reza Aref

doi:10.1109/access.2019.2962101

Siavash Ahmadi, Mohammad Reza Aref

Open Access

https://doi.org/10.1109/access.2019.2962101

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Abstract

Meet in the middle (MITM) attack is one of the most important and applicable methods for cryptanalysis of block ciphers. In this paper, a more generalized method for MITM attack is considered. For this purpose, a notion, namely cut-set, is utilized by which several numbers of MITM attacks can be performed. However, manual investigation on these cases is time-consuming and sometimes not error-free. Therefore, a new search algorithm is also provided to obtain proper attacks in a timely manner. For examination, this new search algorithm, which could make an automated attack along with some certain ideas, is applied on HIGHT, Piccolo-128, CRAFT and AES-128 block ciphers. The least time complexities which are obtained by generalized MITM attack on full HIGHT, Piccolo-128, CRAFT and AES-128 are 2 125.08 , 2 126.78 , 2 123.25 and 2 125.53 , respectively. The results on full-round CRAFT are, to the best of our knowledge, the first cryptanalysis results in the single-key model except the designers' investigations. In addition, the results show some improvements for complexities of all the attacks, especially on HIGHT.

Highlights

Block ciphers are usually the main primitive used for securing communications in various technologies such as cellular networks, internet of things, and so on
CONTRIBUTIONS The purpose of this paper is to express a generalized Meet in the middle (MITM) attack, which can be considered as a general form of some previous attacks, in a way that it could be implemented by an automated search method
Without loss of generality, the master key is chosen for that cut-set

Summary

Introduction

Block ciphers are usually the main primitive used for securing communications in various technologies such as cellular networks, internet of things, and so on. Their security evaluation remains as an important concenteration point of the cryptanalysts. One of the generic methods which is always applied for security evaluation of block ciphers is MITM attack. The basic method was first introduced in [1] for cryptanalysis of DES block cipher, and many variants and improvement techniques for MITM attack were proposed. The basic MITM attack begins from a pair of plaintext/ciphetext, say starting states, and is completed by a matching technique at the middle of a target block cipher, say ending internal/intermediate state. Some of enhanced versions of MITM attack have focused on improving the basic attack by choosing different starting states or promotion of attack structure such as 3-subset MITM [2], splice-and-cut [3], and biclique [4], [5] attacks

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