New results on the genetic cryptanalysis of TEA and reduced-round versions of XTEA

Congress on Evolutionary Computation. Portland, USA, 19-23 June 2004Recently, a simple way of creating very efficient distinguishers for cryptographic primitives such as block ciphers or hash functions, was presented by the authors. Here, this cryptanalysis attack is shown to be successful when applied over reduced round versions of the block cipher XTEA. Additionally, a variant of this genetic attack is introduced and its results over TEA shown to be the most powerful published to date

A Survey of ARX-based Symmetric-key Primitives

Addition Rotation XOR is suitable for fast implementation symmetric –key primitives, such as stream and block ciphers. This paper presents a review of several block and stream ciphers based on ARX construction followed by the discussion on the security analysis of symmetric key primitives where the best attack for every cipher was carried out. We benchmark the implementation on software and hardware according to the evaluation metrics. Therefore, this paper aims at providing a reference for a better selection of ARX design strategy

A Bit-Vector Differential Model for the Modular Addition by a Constant

ARX algorithms are a class of symmetric-key algorithms constructed by Addition, Rotation, and XOR, which achieve the best software performances in low-end microcontrollers. To evaluate the resistance of an ARX cipher against differential cryptanalysis and its variants, the recent automated methods employ constraint satisfaction solvers, such as SMT solvers, to search for optimal characteristics. The main difficulty to formulate this search as a constraint satisfaction problem is obtaining the differential models of the non-linear operations, that is, the constraints describing the differential probability of each non-linear operation of the cipher. While an efficient bit-vector differential model was obtained for the modular addition with two variable inputs, no differential model for the modular addition by a constant has been proposed so far, preventing ARX ciphers including this operation from being evaluated with automated methods. In this paper, we present the first bit-vector differential model for the n-bit modular addition by a constant input. Our model contains O(log2(n)) basic bit-vector constraints and describes the binary logarithm of the differential probability. We also represent an SMT-based automated method to look for differential characteristics of ARX, including constant additions, and we provide an open-source tool ArxPy to find ARX differential characteristics in a fully automated way. To provide some examples, we have searched for related-key differential characteristics of TEA, XTEA, HIGHT, and LEA, obtaining better results than previous works. Our differential model and our automated tool allow cipher designers to select the best constant inputs for modular additions and cryptanalysts to evaluate the resistance of ARX ciphers against differential attacks.acceptedVersio

Impossible Differential Cryptanalysis of the Lightweight Block Ciphers TEA, XTEA and HIGHT

TEA, XTEA and HIGHT are lightweight block ciphers with 64-bit block sizes and 128-bit keys. The round functions of the three ciphers are based on the simple operations XOR, modular addition and shift/rotation. TEA and XTEA are Feistel ciphers with 64 rounds designed by Needham and Wheeler, where XTEA is a successor of TEA, which was proposed by the same authors as an enhanced version of TEA. Whilst HIGHT, which is designed by Hong et al., is a generalized Feistel cipher with 32 rounds and eight 8-bit words in each round. On the one hand, all these ciphers are simple and easy to implement; on the other hand, the diffusion is slow, which allow us to find some impossible properties. This paper proposes a method to identify the impossible differentials for TEA and XTEA by using the diffusion property of these block ciphers, where the impossible differential comes from one bit contradiction. By means of the method, 14-round impossible differential of XTEA and 13-round impossible differential of TEA are derived, which results in improved impossible differential attacks on 23-round XTEA and 17-round TEA, respectively. These attacks significantly improve the previous 11-round impossible differential attack on TEA and 14-round impossible differential attack on XTEA given by Moon et al. from FSE 2002. For HIGHT, we improve the 26-round impossible differential attack proposed by Özen et al.; an impossible differential attack on 27-round HIGHT that is slightly faster that the exhaustive search is also given. The attacks on TEA, XTEA and HIGHT are also the best attacks in terms of time complexity

A Cipher-Agnostic Neural Training Pipeline with Automated Finding of Good Input Differences

Neural cryptanalysis is the study of cryptographic primitives through machine learning techniques. Following Gohr’s seminal paper at CRYPTO 2019, a focus has been placed on improving the accuracy of such distinguishers against specific primitives, using dedicated training schemes, in order to obtain better key recovery attacks based on machine learning. These distinguishers are highly specialized and not trivially applicable to other primitives. In this paper, we focus on the opposite problem: building a generic pipeline for neural cryptanalysis. Our tool is composed of two parts. The first part is an evolutionary algorithm for the search of good input differences for neural distinguishers. The second part is DBitNet, a neural distinguisher architecture agnostic to the structure of the cipher. We show that this fully automated pipeline is competitive with a highly specialized approach, in particular for SPECK32, and SIMON32. We provide new neural distinguishers for several primitives (XTEA, LEA, HIGHT, SIMON128, SPECK128) and improve over the state-of-the-art for PRESENT, KATAN, TEA and GIMLI

Fault-Resilient Lightweight Cryptographic Block Ciphers for Secure Embedded Systems

The development of extremely-constrained environments having sensitive nodes such as RFID tags and nano-sensors necessitates the use of lightweight block ciphers. Indeed, lightweight block ciphers are essential for providing low-cost confidentiality to such applications. Nevertheless, providing the required security properties does not guarantee their reliability and hardware assurance when the architectures are prone to natural and malicious faults. In this thesis, considering false-alarm resistivity, error detection schemes for the lightweight block ciphers are proposed with the case study of XTEA (eXtended TEA). We note that lightweight block ciphers might be better suited for low-resource environments compared to the Advanced Encryption Standard, providing low complexity and power consumption. To the best of the author\u27s knowledge, there has been no error detection scheme presented in the literature for the XTEA to date. Three different error detection approaches are presented and according to our fault-injection simulations for benchmarking the effectiveness of the proposed schemes, high error coverage is derived. Finally, field-programmable gate array (FPGA) implementations of these proposed error detection structures are presented to assess their efficiency and overhead. The proposed error detection architectures are capable of increasing the reliability of the implementations of this lightweight block cipher. The schemes presented can also be applied to lightweight hash functions with similar structures, making the presented schemes suitable for providing reliability to their lightweight security-constrained hardware implementations

Automatic Search for Differential Trails in ARX Ciphers

We propose a tool for automatic search for differential trails in ARX ciphers. By introducing the concept of a partial difference distribution table (pDDT) we extend Matsui's algorithm, originally proposed for DES-like ciphers, to the class of ARX ciphers. To the best of our knowledge this is the first application of Matsui's algorithm to ciphers that do not have S-boxes. The tool is applied to the block ciphers TEA, XTEA, SPECK and RAIDEN. For RAIDEN we find an iterative characteristic on all 32 rounds that can be used to break the full cipher using standard differential cryptanalysis. This is the first cryptanalysis of the cipher in a non-related key setting. Differential trails on 9, 10 and 13 rounds are found for SPECK32, SPECK48 and SPECK64 respectively. The 13 round trail covers half of the total number of rounds. These are the first public results on the security analysis of SPECK. For TEA multiple full (i.e. not truncated) differential trails are reported for the first time, while for XTEA we confirm the previous best known trail reported by Hong et al. We also show closed formulas for computing the exact additive differential probabilities of the left and right shift operations. The source code of the tool is publicly available as part of a larger toolkit for the analysis of ARX at the following address: https://github.com/vesselinux/yaarx

Algoritmos criptográficos e o seu desempenho no Arduíno

O Arduíno é uma plataforma muito robusta e multifacetada utilizada em diversas situações e, cada vez mais, um elemento relevante na arquitetura da Internet das Coisas. Ao disponibilizar várias interfaces de comunicação sem fios, pode ser utilizado para controlar eletrodomésticos, portas, sensores de temperatura, etc. permitindo implementar facilmente a comunicação entre estas “coisas”. Nesta tese foram estudadas as principais redes sem fios utilizadas pelo Arduíno (Bluetooth Low Energy [BLE], Wi-Fi e ZigBee) para tentar perceber qual a que tem o melhor desempenho, vantagens e desvantagens de cada uma, quais os módulos necessários para permitir ao Arduíno utilizar esse tipo de rede sem fios, quais as principais funções para que foram projetadas quando criadas e qual o sistema de segurança utilizado nestas redes. Estas diferentes tecnologias sem fios permitem uma maior mobilidade e uma maior flexibilidade no desenho das estruturas de rede do que as redes com fios convencionais. Porém, este tipo de redes têm uma grande desvantagem já que qualquer um dentro do alcance da rede sem fios consegue intercetar o sinal que está a ser transmitido. Para solucionar e proteger a informação que é transmitida por estas redes foram desenvolvidos vários algoritmos de criptografia. Estes dados encriptados só podem ser lidos por dispositivos que tenham uma determinada chave. Os algoritmos de criptografia Data Encryption Standard (DES), Triple DES (TDES), Advanced Encryption Standard (AES), eXtended TEA (XTEA) Corrected Block TEA (XXTEA) estão entre as técnicas mais conhecidos e usadas tualmente. Nesta tese foram analisados estes algoritmos e as suas vulnerabilidades, tendo também sido feito um levantamento dos principais ataques existentes para avaliar se ainda são seguros atualmente. De forma a avaliar a possibilidade de utilizar o Arduíno em aplicações que utilizem comunicações sem fios com segurança, foram realizados testes de desempenho com os algoritmos de criptografia estudados, usando bibliotecas já existentes. Nos testes de desempenho implementados verificou-se que o AES é bastante mais rápido do que as outras soluções, oferecendo ainda uma maior segurança. Já o TDES verificou-se ser bastante lento, justificando o porquê de o algoritmo ser pouco usado, sendo ao longo dos anos substituído pelo AES. O XXTEA ficou em posição intermédia no teste de desempenho, tendo uma relação segurança/desempenho interessante e revelando-se assim uma escolha melhor do que o TDES.The Arduino is a very robust and multifaceted platform used in many situations and, increasingly, a relevant element in the Internet of Things. By providing several wireless communication interfaces, it can be used to control household appliances, doors, temperature sensors, etc. Allowing easy implementation of communication between these "things". In this thesis the main wireless networks used by Arduino (Bluetooth Low Energy [BLE], Wi-Fi and ZigBee) were studied to try to understand which one has the best performance, the advantages and disadvantages of each one, the modules needed to implement each wireless network and what security system are used. These different wireless technologies allow for greater mobility and greater flexibility in the design of network structures than conventional wired networks. However, such networks have a major disadvantage since anyone within the range of the wireless network can intercept the signal being transmitted. Several cryptographic algorithms have been developed to solve and protect the information that is transmitted by these networks. This encrypted data can only be read by devices that have a certain key. Triple Encryption Standard (DES), Advanced Encryption Standard (AES), eXtended TEA (XTEA) and Corrected Block TEA (XXTEA) encryption algorithms are among the best known and currently used algorithms. In this thesis these algorithms have been analyzed to compare their vulnerabilities and to identify the main existing attacks. In order to evaluate the possibility of using Arduino in applications that use wireless communications with security, performance tests were implemented using existing libraries. The results show that the AES is much faster than the other algorithms, offering even greater security. TDES was found to be quite slow, justifying why the algorithm has little used, and why over the years has been replaced by AES. The XXTEA was ranked in the middle of the performance test, having an interesting safety/performance ratio proving it to be a better choice than TDES