Cryptocurrency based on Blockchain Technology

The state of Palestine does not own national currency so Palestine loses a lot of money yearly due to the use of foreign currencies and the Paris Protocol agreement prevents Palestinian own currency For that the crypto-currencies based on block-chain instead of physical currency will help the state of Palestine to avoid the obstacles that prevent to own currency In this paper we will study the cryptocurrency based on Blockchain technology that uses peer-to-peer P2P and timestamp server In additional exploring the main components of bitcoin currency as an exampl

Joint block and stream cipher based on a modified skew tent map

Image encryption is very different from that of texts due to the bulk data capacity and the high redundancy of images. Thus, traditional methods are difficult to use for image encryption as their pseudo-random sequences have small space. Chaotic cryptography use chaos theory in specific systems working such as computing algorithms to accomplish dissimilar cryptographic tasks in a cryptosystem with a fast throughput. For higher security, encryption is the approach to guard information and prevent its leakage. In this paper, a hybrid encryption scheme that combines both stream and block ciphering algorithms is proposed in order to achieve the required level of security with the minimum encryption time. This scheme is based on an improved mathematical model to cover the defects in the previous discredited model proposed by Masuda. The proposed chaos-based cryptosystem uses the improved Skew Tent Map (STM) RQ-FSTM as a substitution layer. This map is based on a lookup table to overcome various problems, such as the fixed point, the key space restrictions, and the limitation of mapping between plain text and cipher text. It uses the same map as a generator to change the byte position to achieve the required confusion and diffusion effects. This modification improves the security level of the original STM. The robustness of the proposed cryptosystem is proven by the performance and the security analysis, as well as the high encryption speed. Depending on the results of the security analysis the proposed system has a better dynamic key space than previous ones using STM, a double encryption quality and a better security analysis than others in the literature with speed convenience to real-time applications

Crypto-systèmes basés chaos et systèmes de crypto-compression

The security of image and video data is important formany applications which require in real-time a highsecurity level. In the first part of this work, fourchaos-based cryptosystems, flexible, efficient, andmore robust against cryptanalysis, are designed andrealized. The first two cryptosystems are based on thesubstitution-permutation network. The substitution isachieved by a proposed modified Finite Skew TentMap (FSTM) to overcome various problems: fixedpoint, key space restriction, and limitation of mappingbetween plaintext and ciphertext. The thirdcryptosystem is a new and efficient structure. It isbased on a binary diffusion layer of pixels, followed bya bit-permutation layer. The permutation is achievedby an efficient proposed formulation of the 2-D catmap. The fourth cryptosystem is faster than theothers, having a very high security level. Theconfusion and the diffusion are performed in a singlescan. Its design is based on a partial cryptanalysisthat we performed on the Zhang algorithm. In thesecond part, two fast and secure selectivechaos-based crypto-compressions are designed andrealized to secure the High Efficiency Video Coding(HEVC) and its scalable version. In the firstcrypto-compression, a new algorithm is proposed todefine the encryptable bits in the bit stream of theHEVC and the SHVC systems. The proposed solutionencrypts a set of sensitive SHVC parameters at theentropy encoder (CABAC), while preserving all SHVCfunctionalities. Based on the tile concept, the secondproposed crypto-compression provides protection ofthe ROI defined in the standard HEVC.La sécurité des données images et vidéos estimportante pour beaucoup d’applications qui exigentdu temps réel et un haut niveau de sécurité. Dans lapremière partie de ce travail, quatre cryptosystèmesbasés chaos flexibles, efficaces et très robustes contrela cryptanalyse sont conçus et réalisés. Les deuxpremiers s’appuient sur le réseau SPN. La substitutionest réalisée par une carte Skew tent (FSTM) modifiéepour surmonter différents problèmes : point fixe,restriction de la taille de la clé et limitation de lacartographie entre les textes d’origines et chiffrés. Letroisième cryptosystème est de structure nouvelle etégalement efficace. Il est basé sur une couche dediffusion binaire de pixels, suivi par une couche depermutation des bits. La permutation est réalisée parune nouvelle formulation efficace de la carte 2-D Cat.Le quatrième cryptosystème, est plus rapide que lesautres avec un niveau de sécurité très élevé. Saconception s’appuie sur une cryptanalyse partielle,que nous avons réalisée, de l’algorithme de Zhang.Dans la deuxième partie, deux crypto-compressionbasés chaos sélectifs et rapides sont utilisés poursécuriser le flux HEVC et SHVC. Dans le premiercrypto-compression, un nouvel algorithme pour définirles bits chiffrables dans le flux binaire du HEVC et duSHVC est proposé. La solution proposée chiffre unensemble de paramètres SHVC sensibles au niveaudu codeur entropique (CABAC), tout en préservantl’ensemble des fonctionnalités SHVC. Basé sur leconcept de tuile, le deuxième crypto-compressionproposé permet une protection de la vidéo au niveaud’une Région d’Intérêt (ROI) définie dans le standardHEVC

A New chaos-based image encryption system

International audienceDuring the last decade, a variety of chaos-based cryptosystems has been introduced toprotect the content of the transmitted images. In this paper, we propose a new fast, simple, and robustchaos-based cryptosystem structure and we analyze its performances. The cryptosystem uses adiffusion layer followed by a bit-permutation layer, instead of byte-permutation, to shuffle thepositions of the image pixels. Moreover, the permutation layer is achieved by a new proposedformulation of the 2D cat map that allows an efficient implementation, measured by the timecomplexity, in terms of arithmetic and logic operations, and also, in terms of clock cycles, of the keydependentpermutation process in comparison with the standard one. Hence, it provides a very fastdiffusion process to spread the influence of a single bit over the others. The new cryptosystem includesa robust and uniform chaotic pseudo-random generator (a very simplified version of a generatorpublished in our patent) to change the control parameters in each round of the encryption/decryptionprocesses. The generator is highly nonlinear and produces robust sequences of discrete values havingvery long orbits. The proposed cryptosystem is defined on finite numbers, and its speed is faster thanmany chaos-based cryptosystems, while having a very high security level. The security analysis and theobtained simulation results show that the proposed cryptosystem is resistant to various types ofattacks and it is efficient for hardware and software implementation

Dynamic adjustment of the chaos-based security in real-time energy harvesting sensors

International audienc

Fast and secure chaos-based cryptosystem for images

International audienceNon-linear dynamic cryptosystems or chaos-based cryptosystems have been attracting a large amount of research since 1990. The critical aspect of cryptography is to face the growth of communication and to achieve the design of fast and secure cryptosystems. In this paper, we introduce three versions of a chaos-based cryptosystem based on a similar structure of the Zhang and Fridrich cryptosystems. Each version is composed of two layers: a confusion layer and a diffusion layer. The confusion layer is achieved by using a modified 2-D cat map to overcome the fixedpoint problem and some other weaknesses, and also to increase the dynamic key space. The 32-bit logistic map is used as a diffusion layer for the first version, which is more robust than using it in 8-bit. In the other versions, the logistic map is replaced by a modified Finite Skew Tent Map (FSTM) for three reasons: to increase the nonlinearity properties of the diffusion layer, to overcome the fixed-point problem, and toincrease the dynamic key space. Finally, all versions of the proposed cryptosystem are more resistant against known attacks and faster thanZhang cryptosystems. Moreover, the dynamic key space is much larger than the one used in Zhang cryptosystems. Performance and security analysis prove that the proposed cryptosystems are suitable for securing real-time applications

Dynamic adjustment of the chaos-based security in real-time energy harvesting sensors

International audienc

Chaos-based Block Ciphers: An Overview

International audienceA variety of chaos-based cryptosystems have been investigated during the last decade. Most of them are based on the structure of Fridrich, which is based on the traditional confusion-diffusion architecture proposed by Shannon. Compared with traditional cryptosystems (DES, 3DES, AES, etc.), the chaos-based cryptosystems are more flexible, more modular and easier to be implemented, which make them more suitable for large scale-data encryption, such as images and videos. The heart of any chaos-based cryptosystem is the chaotic generator and so, a part of the efficiency (robustness, speed) of the system depends greatly on it. In this talk, we give an overview of the state of the art of chaos-based block ciphers and we describe some of our schemes already proposed. Also, we will focus on the essential characteristics of the digital chaotic generator that we published in October 2011 as a French patent and also we published in 2013 an extension of the patent in Europe, China, Japan, and USA. The needed performance of a chaos-based block cipher in terms of security level and speed of calculus depends on the considered application. There is a compromise between the security and the speed of the calculation. The security of these block ciphers will be analyzed

Cryptanalyzing an image encryption scheme using reverse 2-dimensional chaotic map and dependent diffusion

International audienceIn the recent literature, many research studies have proven that Known and Chosen plaintext attacks are very efficient tools that are widely used to cryptanalyze partially or completely some chaos-based and non-chaos cryptosystems. In this paper, we addressed some weaknesses in the first Zhang et al., cryptosystem “An image encryption scheme using reverse 2-dimensional chaotic map and dependent diffusion”. First, we analyzed the encryption process of Zhang et al., and we found that the non-linear diffusion process can be removed because its argument is present in the ciphered image. Then, based on this observation we derived a partial cryptanalysis equation that removes the effect of the diffusion function and accordingly permits to recover the permuted version of the ciphered image. As a result of the previous operation, the brute-force attack became more suitable. In addition, we mounted a chosen plaintext attack based on a proposed chosen plain image. Consequently, the encryption key space is reduced or recovered for one round, also, the average values of NPCR and UCAI randomness parameters become small compared to the optimal values, and moreover, they are very low for specific pixel position attacks