Cryptanalysis Research Articles

Security Analysis of SKINNY under Related-Tweakey Settings

In CRYPTO’16, a new family of tweakable lightweight block ciphers - SKINNY was introduced. Denoting the variants of SKINNY as SKINNY-n-t, where n represents the block size and t represents the tweakey length, the design specifies t ∈ {n, 2n, 3n}. In this work, we evaluate the security of SKINNY against differential cryptanalysis in the related-tweakey model. First, we investigate truncated related-tweakey differential trails of SKINNY and search for the longest impossible and rectangle distinguishers where there is only one active cell in the input and the output. Based on the distinguishers obtained, 19, 23 and 27 rounds of SKINNY-n-n, SKINNY-n-2n and SKINNY-n-3n can be attacked respectively. Next, actual differential trails for SKINNY under related-tweakey model are explored and optimal differential trails of SKINNY-64 within certain number of rounds are searched with an indirect searching method based on Mixed-Integer Linear Programming. The results show a trend that as the number of rounds increases, the probability of optimal differential trails is much lower than the probability derived from the lower bounds of active Sboxes in SKINNY.

Development of the approach to proving the security of block ciphers to impossible differential attack

Trends in the development of symmetric cryptography are constantly associated with the increasing of the sizes of keys and blocks. Block ciphers, which are used today in hashing algorithms, usually have a block size of 512 or 1024 bits. One of the main requirements for symmetric crypto algorithms is to provide resistance to known cryptanalytical attacks. Known methods of security estimation against impossible differential attack have too high complexity for such block sizes. The proposed approach for proving the absence of impossible differentials is applicable to some types of block ciphers and allows proving theoretically the resistance to impossible differentials attack. Rijndael-like SPN ciphers and Feistel ciphers are analyzed. For the group of Rijndael-like ciphers, the absence of byte impossible differentials for 4 or more rounds is proved. For the group of Feistel ciphers, the absence of byte impossible differentials for 6 or more rounds is proved. The first statement made it possible to prove the absence of byte impossible differentials for 4 or more rounds of the cipher Kalyna (DSTU 7624: 2014) with all block sizes, for 512-bit block ciphers that are used in the hash functions Whirlpool, Groestl and Kupyna (DSTU 7564: 2014). The second statement was used to prove the absence of byte impossible differentials for 6 or more rounds of Tornado and Labyrinth ciphers with a block size of 128 bits. Computational experiments on the impossible differentials search for these reduced models confirmed the validity of the obtained theoretical conclusions

Improved cryptanalysis of step-reduced SM3

Improved cryptanalysis of step-reduced SM3

Development of 2D implicit particle simulation code for ohmic breakdown physics in a tokamak

A physical mechanism of an ohmic breakdown in a tokamak has not been clearly understood due to its complexity in physics and geometry especially for a role of space charge in the plasma. We have developed a 2D implicit particle simulation code BREAK, to study the ohmic breakdown physics under a realistic complicated situation considering the space charge and kinetic effects consistently. The ohmic breakdown phenomena span a broad range of spatio-temporal scales, from picoseconds order of the electron gyromotion to milliseconds order of the plasma transport. It is impossible to employ a typical explicit particle simulation method to see the slow plasma transport phenomena of our interest, because a time step size is restricted to be smaller than a period of the electron gyromotion in the explicit scheme. Hence, we adopt several physical and numerical models, such as a toroidally symmetric model and a direct-implicit method, to relax or remove the spatio-temporal restrictions. In addition, coalescence strategies are introduced to control the number of numerical super particles within acceptable ranges to handle the exponentially growing plasma density during the ohmic breakdown. The performance of BREAK is verified with several test cases so that BREAK is expected to be applicable to investigate the ohmic breakdown physics in the tokamak by considering 2-dimensional plasma physics in the RZ plane, self-consistently.

Crypt analysis of an image compression–encryption algorithm and a modified scheme using compressive sensing

Compressive sensing acquires image in the form of linear measurements. Utilizing compressive sensing in image encryption makes most of the algorithm vulnerable, due to the linearity property of compressive sensing retained in the encryption process. In this paper, a compression–encryption algorithm based on compressive sensing is analysed. It is demonstrated that chosen plain-text attack can be performed successfully for the scheme mentioned above. This paper shows that the encryption combined with compression adapted in the scheme under analysis can be represented as a single linear transformation. The corresponding matrix of transformation can be computed using the chosen plain-text attack. This matrix enables to encrypt or decrypt any image without knowing the keys. A modified scheme is proposed in which the encryption process is designed to change dynamically depending on the values of the plain image. The dynamic nature of the scheme makes it nonlinear and hence the scheme is secure against the chosen plain text attack.

Discrete linear models for the generalized self-shrunken sequences

In this work, different decimation-based sequence generators for cryptographic purposes have been analyzed in detail. In fact, the modified self-shrinking generator was first introduced as an improved version of the self-shrinking generator. However, it is here proven that the sequences produced by both generators belong to the same family of sequences, that is the class of the generalized self-shrinking sequences. Thus, both sequences have the same properties as well as the same weaknesses. Moreover, such sequences can be generated by linear structures based on one-dimensional cellular automata. The linearity inherent to the cellular automata-based models can be used to launch a cryptanalytic attack against such non-linear generators.

Information Security using Adaptive Multidimensional Playfair Cipher

Confidential information in today’s world exists in many forms such as text, image, audio, video, encoded, compressed etc. The important aim of this research is to develop such a cryptographic cipher which is very strong and can secure all types of information without any ambiguity. It is discovered from survey that the existing variations of Playfair cipher except one can support securing limited number of characters and most of them are ambiguous, have less confusion rate and avalanche effect which should be high in order to be strong. Exceptional variation is the one that supported securing all types of information without ambiguity. Unfortunately, this variation is not memory and bandwidth efficient like many other variants and it can have low or moderate avalanche effect with respect to one bit change in plain message. So, we propose a new variant called Adaptive Multidimensional Playfair Cipher (AMPC) which can secure all types of information unambiguously with high confusion rate and avalanche effect, and is memory and bandwidth efficient. The security analysis of the proposed cipher shows that it is strong against five major types of cryptanalytic attacks. The comparison analysis shows that the proposed cipher is better than the existing variations in terms of memory utilization, security and applicability.

Cryptanalytic attacks on cyber-physical systems

Cryptography finds its application in various objects used in our everyday life. GSM communication, credit cards, tickets for public transport or RFID tags employ cryptographic features either to protect privacy or to ensure trustworthy authentication. However, many such objects are vulnerable to certain cryptanalytic attacks. In this review we discuss how FPGA-based cryptanalytic hardware may compromise GSM communication, or how standard laboratory equipment may be used for breaking Smart Card security. This review summarizes keynote speech that was given at 5th Mediterranean Conference on Embedded Computing (MECO’2016).

Design of Lightweight Linear Diffusion Layers from Near-MDS Matrices

Near-MDS matrices provide better trade-offs between security and efficiency compared to constructions based on MDS matrices, which are favored for hardwareoriented designs. We present new designs of lightweight linear diffusion layers by constructing lightweight near-MDS matrices. Firstly generic n × n near-MDS circulant matrices are found for 5 ≤ n ≤9. Secondly, the implementation cost of instantiations of the generic near-MDS matrices is examined. Surprisingly, for n = 7 , 8, it turns out that some proposed near-MDS circulant matrices of order n have the lowest XOR count among all near-MDS matrices of the same order. Further, for n = 5 , 6, we present near-MDS matrices of order n having the lowest XOR count as well. The proposed matrices, together with previous construction of order less than five, lead to solutions of n × n near-MDS matrices with the lowest XOR count over finite fields F 2 m for 2 ≤ n ≤ 8 and 4 ≤ m ≤ 2048. Moreover, we present some involutory near-MDS matrices of order 8 constructed from Hadamard matrices. Lastly, the security of the proposed linear layers is studied by calculating lower bounds on the number of active S-boxes. It is shown that our linear layers with a well-chosen nonlinear layer can provide sufficient security against differential and linear cryptanalysis.

A New Algorithm for Encrypting Arabic text Using the Mathematical Equation

Most organizations today use two levels of security: Data security level (encryption) and Network security level (firewall) etc. Therefore, encryption plays a vital role in securing daily operations of organizations. Securing data at first level aims to hide data characteristics. So, different algorithms and methods are being researched and developed to cover this gap for securing different data types especially text messages and make it very difficult for unauthorized parties to break it. From these, the major no. of algorithms are specialized to encrypt English texts, but no one for Arabic language texts although there were many attempts to invent such algorithms. As a result, this research proposed a new encryption method to encrypt Arabic text by using the principle of integration to provide better security and increasing the complexity of guessing the correct keys and correct plain text. At the end, the results show that the new cryptosystem is inevitable to cryptanalysis attack.

A Stream Cipher based on Spatiotemporal Chaos and True Random Synchronization

ABSTRACTStream ciphers require the use of initialization vectors (IVs) to ensure that the same secret key produces different keystreams. It also synchronizes communication between two parties. However, there are many cryptanalytic attacks that exploit weaknesses in the IV setup of stream ciphers. In an effort to solve this problem, we introduce a chaos-based stream cipher that utilizes a new mode of synchronization called true random synchronization (TRSync). The stream cipher is designed based on spatiotemporal chaos while taking advantage of TRSync to resist various statistical attacks. The stream cipher operations also include data-dependent rotations and chaotic perturbation. As chaotic functions are inherently slow due to floating point operations, we utilize fixed point representation for higher efficiency. TRSync includes a true random number sequence (TRNS) into the synchronization process alongside the public IV. The IV is masked by the TRNS before being used to setup the cipher. Therefore, the cipher's internal state cannot be manipulated by an attacker and constantly changes even if the secret key-IV pairs are constant. TRSync can also be used to secure other stream ciphers with IVs as described in this paper. The security of the proposed chaotic cipher is thoroughly analyzed in terms of randomness, periodicity, entropy, balance, correlation, and complexity.

Increasing robustness of data encryption standard by integrating DNA cryptography

Encryption has become a necessity of life, especially in the field of exchanging and transmitting data through transmission media, such as internet, wireless networks, mobile networks, bluetooth, and infrared. The deoxyribonucleic acid (DNA) cryptography is a very promising approach which is shown to be efficient in computation, storage, and transmission. In this paper, we introduce a new technique for encryption called DNA-DES that is more robust than traditional data encryption standard (DES). The proposed technique integrates concepts derived from DNA, ribonucleic acid, and nucleic acids to increase the key space and number of available permutations of traditional DES. The theoretical and experimental analysis show that the proposed DNA-DES method is efficient in computation, storage, and transmission. The security analysis proves that DNA-DES has high confidential strength against brute-force and cryptanalysis attacks.

A novel approach with matrix based public key crypto systems

Here in this model, a new mechanism is used for Public Key Cryptography. A generator matrix is used to generate a field with a large prime number. The generator matrix, prime number and quaternary vector are used as global variables. The Generator Matrix is powered by a private key to generate Public Key. Since the model is based on Discrete Logarithm Problem, which is Hard problem, the proposed algorithm supports the features like Authenticity of users, Security & Confidentiality of data transmitted.Going by the construction of the algorithm, Encryption is being done on blocks of data for which it consumes less computing resources. Going by complexity of the algorithm, the key length needed is about 72 bit lengths to provide sufficient strengths against crypto analysis.

Significantly Improved Multi-bit Differentials for Reduced Round Salsa and ChaCha

ChaCha and Salsa are two software oriented stream ciphers that have attracted serious attention in academic as well as commercial domain. The most important cryptanalysis of reduced versions of these ciphers was presented by Aumasson et al. in FSE 2008. One part of their attack was to apply input difference(s) to investigate biases after a few rounds. So far there have been certain kind of limited exhaustive searches to obtain such biases. For the first time, in this paper, we show how to theoretically choose the combinations of the output bits to obtain significantly improved biases. The main idea here is to consider the multi-bit differentials as extension of suitable single-bit differentials with linear approximations, which is essentially a differential-linear attack. As we consider combinations of many output bits (for example 19 for Salsa and 21 for ChaCha), exhaustive search is not possible here. By this method we obtain very high biases for linear combinations of bits in Salsa after 6 rounds and in ChaCha after 5 rounds. These are clearly two rounds of improvement for both the ciphers over the existing works. Using these biases we obtain several significantly improved cryptanalytic results for reduced round Salsa and ChaCha that could not b obtained earlier. In fact, with our results it is now possible to cryptanalyse 6-round Salsa and 5-round ChaCha in practical time.

Cryptanalytic study of property-preserving encryption

Cryptanalytic study of property-preserving encryption

Digital Implementation of an Improved LTE Stream Cipher Snow-3G Based on Hyperchaotic PRNG

SNOW-3G is a stream cipher used by the 3GPP standards as the core part of the confidentiality and integrity algorithms for UMTS and LTE networks. This paper proposes an enhancement of the regular SNOW-3G ciphering algorithm based on HC-PRNG. The proposed cipher scheme is based on hyperchaotic generator which is used as an additional layer to the SNOW-3G architecture to improve the randomness of its output keystream. The objective of this work is to achieve a high security strength of the regular SNOW-3G algorithm while maintaining its standardized properties. The originality of this new scheme is that it provides a good trade-off between good randomness properties, performance, and hardware resources. Numerical simulations, hardware digital implementation, and experimental results using Xilinx FPGA Virtex technology have demonstrated the feasibility and the efficiency of our secure solution while promising technique can be applied to secure the new generation mobile standards. Thorough analysis of statistical randomness is carried out demonstrating the improved statistical randomness properties of the new scheme compared to the standard SNOW-3G, while preserving its resistance against cryptanalytic attacks.

A Multi-Threaded Symmetric Block Encryption Scheme Implementing PRNG for DES and AES Systems

Due to the ever-increasing efficiency of computer systems, symmetric cryptosystem are becoming more vulnerable to linear cryptanalysis brute force attacks. For example, DES with its short key (56 bits) is becoming easier to break, while AES has a much longer key size (up to 256 bits), which makes it very difficult to crack using even the most advanced dedicated cryptanalysis computers. However, more complex algorithms, which exhibit better confusion and diffusion characteristics, are always required. Such algorithms must have stronger resistance against differential and linear cryptanalysis attacks. This paper describes the development of an algorithm that implements a pseudo random number generator (PRNG) in order to increase the key generation complexity. Experimental results on both DES and AES cryptosystems complemented with the PRNG have shown an average improvement of up to 36.3% in the avalanche error computation over the original standard systems, which is a considerable improvement in the time complexity of both systems.

Chaotic S‐Box: Intertwining Logistic Map and Bacterial Foraging Optimization

As the unique nonlinear component of block ciphers, Substitution box (S‐box) directly affects the safety of a cryptographic system. It is important and difficult to design strong S‐box that simultaneously meets multiple cryptographic criteria such as bijection, nonlinearity, strict avalanche criterion (SAC), bit independence criterion (BIC), differential probability (DP), and linear probability (LP). Though many chaotic S‐boxes have been proposed, the cryptographic performance of most of them needs to be further improved. A new chaotic S‐box based on the intertwining logistic map and bacterial foraging optimization is designed in this paper. It firstly iterates the intertwining logistic map to construct many S‐boxes and then applies a bacterial foraging optimization algorithm to find the optimal S‐box. Moreover, bacterial foraging optimization algorithm considers the nonlinearity and differential uniformity as the fitness functions in the optimization process. We experiment that the proposed S‐box can effectively resist multiple types of cryptanalysis attacks.

Online luxury: The code breakers of a traditional sector

In the recent years, the Internet has been a key factor in the evolution of globalization. Allowing a development at a speed, which have never been seen before, it completely revolutionized the way we exchange, communicate, trade and buy. Luxury, which has been a traditional market for thousands of years without ever seeing many changes, couldn’t be spared from such a life-changing discovery. Here is the concern, how to match those two words which, at a glance, have nothing to do in common? Not only how to adapt the Internet to the luxury world, but also how to adapt luxury to the Internet? More than this, until which level can they both be adapted without being denaturalized?From a branding point of view, the challenge is already determinant and we will try to answer these questions in our research. On the other side, we get the customers. Indeed, from a traditional segmentation, the Internet opened the way for a new type of customers to play a huge role in the luxury industry. We can therefore wonder who those customers are. What are they waiting for in terms of service? How do you match the customer expectations while staying coherent with your brand?More than a debate about luxury and the Internet, we can extrapolate this subject as a way of dealing with tradition and modernism, and how initial challenges can create opportunities to reach new territories and create amazing brand experiences.

A Hybrid Chaotic and Number Theoretic Approach for Securing DICOM Images

The advancements in telecommunication and networking technologies have led to the increased popularity and widespread usage of telemedicine. Telemedicine involves storage and exchange of large volume of medical records for remote diagnosis and improved health care services. Images in medical records are characterized by huge volume, high redundancy, and strong correlation among adjacent pixels. This research work proposes a novel idea of integrating number theoretic approach with Henon map for secure and efficient encryption. Modular exponentiation of the primitive roots of the chosen prime in the range of its residual set is employed in the generation of two-dimensional array of keys. The key matrix is permuted and chaotically controlled by Henon map to decide the encryption keys for every pixel of DICOM image. The proposed system is highly secure because of the randomness introduced due to the application of modular exponentiation key generation and application of Henon maps for permutation of keys. Experiments have been conducted to analyze key space, key sensitivity, avalanche effect, correlation distribution, entropy, and histograms. The corresponding results confirm the strength of the proposed design towards statistical and differential crypt analysis. The computational requirements for encryption/decryption have been reduced significantly owing to the reduced number of computations in the process of encryption/decryption.