A new meet-in-the-middle attack on the IDEA block cipher

In this paper we introduce a novel meet-in-the-middle attack on the IDEA block cipher. The attack consists of a precomputation and an elimination phase. The attack reduces the number of required plaintexts significantly for 4 and 4.5 rounds, and, to the best of our knowledge, it is the first attack on the 5-round IDEA. © Springer-Verlag Berlin Heidelberg 2004

New Attacks against Reduced-Round Versions of IDEA

In this paper, we describe a sequence of simple, yet e cient chosen-plaintext (or chosen-ciphertext) attacks against reduced-round versions of IDEA (with 2, 2.5, 3, 3.5, and 4 rounds) which compare favourably with the best known attacks: some of them decrease considerably the time complexity given the same order of data at disposal while other ones decrease the amount of necessary known- or chosen-plaintext pairs under comparable time complexities. Additionally, we show how to trade time and memory for some of the known-plaintext attacks of Nakahara et al

Improved DST cryptanalysis of IDEA

In this paper, we show how the Demirci-Selcuk-Ture attack, which is currently the deepest penetrating attack on the IDEA block cipher, can be improved significantly in performance. The improvements presented reduce the attack's plaintext, memory, precomputation time, and key search time complexities. These improvements also make a practical implementation of the attack on reduced versions of IDEA possible, enabling the first experimental verifications of the DST attack. © Springer-Verlag Berlin Heidelberg 2007

Cryptoraptor : high throughput reconfigurable cryptographic processor for symmetric key encryption and cryptographic hash functions

textIn cryptographic processor design, the selection of functional primitives and connection structures between these primitives are extremely crucial to maximize throughput and flexibility. Hence, detailed analysis on the specifications and requirements of existing crypto-systems plays a crucial role in cryptographic processor design. This thesis provides the most comprehensive literature review that we are aware of on the widest range of existing cryptographic algorithms, their specifications, requirements, and hardware structures. In the light of this analysis, it also describes a high performance, low power, and highly flexible cryptographic processor, Cryptoraptor, that is designed to support both today's and tomorrow's encryption standards. To the best of our knowledge, the proposed cryptographic processor supports the widest range of cryptographic algorithms compared to other solutions in the literature and is the only crypto-specific processor targeting the future standards as well. Unlike previous work, we aim for maximum throughput for all known encryption standards, and to support future standards as well. Our 1GHz design achieves a peak throughput of 128Gbps for AES-128 which is competitive with ASIC designs and has 25X and 160X higher throughput per area than CPU and GPU solutions, respectively.Electrical and Computer Engineerin

Statistical cryptanalysis of block ciphers

Since the development of cryptology in the industrial and academic worlds in the seventies, public knowledge and expertise have grown in a tremendous way, notably because of the increasing, nowadays almost ubiquitous, presence of electronic communication means in our lives. Block ciphers are inevitable building blocks of the security of various electronic systems. Recently, many advances have been published in the field of public-key cryptography, being in the understanding of involved security models or in the mathematical security proofs applied to precise cryptosystems. Unfortunately, this is still not the case in the world of symmetric-key cryptography and the current state of knowledge is far from reaching such a goal. However, block and stream ciphers tend to counterbalance this lack of "provable security" by other advantages, like high data throughput and ease of implementation. In the first part of this thesis, we would like to add a (small) stone to the wall of provable security of block ciphers with the (theoretical and experimental) statistical analysis of the mechanisms behind Matsui's linear cryptanalysis as well as more abstract models of attacks. For this purpose, we consider the underlying problem as a statistical hypothesis testing problem and we make a heavy use of the Neyman-Pearson paradigm. Then, we generalize the concept of linear distinguisher and we discuss the power of such a generalization. Furthermore, we introduce the concept of sequential distinguisher, based on sequential sampling, and of aggregate distinguishers, which allows to build sub-optimal but efficient distinguishers. Finally, we propose new attacks against reduced-round version of the block cipher IDEA. In the second part, we propose the design of a new family of block ciphers named FOX. First, we study the efficiency of optimal diffusive components when implemented on low-cost architectures, and we present several new constructions of MDS matrices; then, we precisely describe FOX and we discuss its security regarding linear and differential cryptanalysis, integral attacks, and algebraic attacks. Finally, various implementation issues are considered

A Salad of Block Ciphers

This book is a survey on the state of the art in block cipher design and analysis. It is work in progress, and it has been for the good part of the last three years -- sadly, for various reasons no significant change has been made during the last twelve months. However, it is also in a self-contained, useable, and relatively polished state, and for this reason I have decided to release this \textit{snapshot} onto the public as a service to the cryptographic community, both in order to obtain feedback, and also as a means to give something back to the community from which I have learned much. At some point I will produce a final version -- whatever being a ``final version\u27\u27 means in the constantly evolving field of block cipher design -- and I will publish it. In the meantime I hope the material contained here will be useful to other people

SoK: Security Evaluation of SBox-Based Block Ciphers

Cryptanalysis of block ciphers is an active and important research area with an extensive volume of literature. For this work, we focus on SBox-based ciphers, as they are widely used and cover a large class of block ciphers. While there have been prior works that have consolidated attacks on block ciphers, they usually focus on describing and listing the attacks. Moreover, the methods for evaluating a cipher\u27s security are often ad hoc, differing from cipher to cipher, as attacks and evaluation techniques are developed along the way. As such, we aim to organise the attack literature, as well as the work on security evaluation. In this work, we present a systematization of cryptanalysis of SBox-based block ciphers focusing on three main areas: (1) Evaluation of block ciphers against standard cryptanalytic attacks; (2) Organisation and relationships between various attacks; (3) Comparison of the evaluation and attacks on existing ciphers

New Data-Efficient Attacks on Reduced-Round IDEA

IDEA is a 64-bit block cipher with 128-bit keys which is widely used due to its inclusion in several cryptographic packages such as PGP. After its introduction by Lai and Massey in 1991, it was subjected to an extensive cryptanalytic effort, but so far the largest variant on which there are any published attacks contains only 6 of its 8.5-rounds. The first 6-round attack, described in the conference version of this paper in 2007, was extremely marginal: It required essentially the entire codebook, and saved only a factor of 2 compared to the time complexity of exhaustive search. In 2009, Sun and Lai reduced the data complexity of the 6-round attack from 2^{64} to 2^{49} chosen plaintexts and simultaneously reduced the time complexity from 2^{127} to 2^{112.1} encryptions. In this revised version of our paper, we combine a highly optimized meet-in-the-middle attack with a keyless version of the Biryukov-Demirci relation to obtain new key recovery attacks on reduced-round IDEA, which dramatically reduce their data complexities and increase the number of rounds to which they are applicable. In the case of 6-round IDEA, we need only two known plaintexts (the minimal number of 64-bit messages required to determine a 128-bit key) to perform full key recovery in 2^{123.4} time. By increasing the number of known plaintexts to sixteen, we can reduce the time complexity to 2^{111.9}, which is slightly faster than the Sun and Lai data-intensive attack. By increasing the number of plaintexts to about one thousand, we can now attack 6.5 rounds of IDEA, which could not be attacked by any previously published technique. By pushing our techniques to extremes, we can attack 7.5 rounds using 2^{63} plaintexts and 2^{114} time, and by using an optimized version of a distributive attack, we can reduce the time complexity of exhaustive search on the full 8.5-round IDEA to 2^{126.8} encryptions using only 16 plaintexts