جستجوی مقالات مرتبط با کلیدواژه "cryptography" در نشریات گروه "پدافند غیرعامل"

The Secret sharing is one of the fascinating topics of cryptography, which is widely used in information security. The aim of secret sharing is a process in which one or more secrets are shared between a number of qualified participants or with different credentials. In times when there is a need to recover a secret, a number of people, whom we call authorized people, collect their shares to recover the desired secret. So far, various types of secret sharing schemes based on interpolation have been proposed. In these secret sharing plans, different interpolations have been used, depending on the structural needs of the plan. In this article, some secret sharing schemes based on interpolation are introduced and reviewed. Then by analyzing and comparing the characteristics of these schemes, we conclude that the two secret sharing schemes based on Berkhoff interpolation have better efficiency than the other reviewed schemes.

One of the most important information security techniques is the hiding of information. Steganography is the art and science of hiding information in the cover of data (in the form of text, image, video, or audio) such that it does not arise any suspicions, and is difficult or even impossible to discover. This paper presents a method for steganography in the form of text which uses the methods of text justifying in typing editors. The method presented in this paper is able to hide information better than some of previous algorithms in this field. This algorithm is resistant to various forms of attack such as visual, structural and statistical attacks. Another important capability of this method is that it can be used to send printed information.

One of the dangers that is inflicted to the world by quantum algorithms is their usage to break the security of some systems based on classical cryptography. Nonetheless, the security of systems based on quantum cryptographic algorithms is safe from this risk. Another useful feature of quantum cryptography algorithms is the ability to figuring out any eavesdropping in the communication channel. Also, it is possible to safely distribute shares from the stock maker to the shareholders in the quantum secret sharing algorithm, while this is not possible in the classic secret sharing algorithm. One of the most important applications of the Internet of Things (IoT) network is the Military Internet of Things (MIoT). Due to the fact that MIoT has a direct impact on battlefields, military usage of IoT is more important than civilian applications. Therefore, security issues related to various parts of the MIoT are very critical. In this paper, we have presented a new design using a combination of classical cryptography (specifically the newly introduced digital signature scheme) and quantum cryptography (specifically quantum secret sharing) to improve the security of MIoT. Compared to similar research that have been conducted in this area, the introduced scheme provides more security requirements and is resistant to almost most of famous attacks on this network.

The network overhead and multiple networks disconnection faults are the main challenges of anonymous servers  implemented in VANETs. The block chain technology has been entered into the wide range of preserving privacy. The robust anonymity mechanism existence and the traceability of all transactions are the main advantages of this  technology. The primary model of the block chain was able to complete the process with the anonymity stored data. In distributed models, the authentication, storage and retrieval of transactions are applied by all user’s consensus. The asymmetric cryptography, preserves the identity anonymity and aggregating transactions of different users into a block which is ready to send, preserves the path anonymity. The proposed method is aimed to ensure anonymity by mounting the block chain on VANETs. Before delivering any transaction to the block chain, the risk of user’s privacy is high. To achieve low risk, we combine the graph processing methods with Silent Period, Cloaking-Region and  Dummy Node methods. The block chain simulation on VANET is driven by python and the anonymity risks are simulated with ARX. The results suggest that the block chain is stabled and the optimal risk reduction is achieved on the VANET.

In the present era, along with the spread of technology in different fields and the possibility of remotely accomplishing different tasks and using internal networks and the Internet, related problems and challenges have occurred. One of these problems is maintaining the security of information while sending and receiving, to prevent unauthorized access. Watermarking is the science of hiding and covering the information with the highest degree of accuracy in security, in order to securely transfer information between the points of interest, so that even when an unauthorized access happens, there is no access to the watermarked data. There are two important features in watermarking. First, the information embedding should not make significant changes in the host environment, and second, the statistical properties of the cover image and the message should be as close as possible in order to have better cryptography. The main purpose of this paper is to provide a new method based on discrete wavelet transform to achieve a suitable cryptographic method. In this method, based on wavelet transforms, color images are watermarked so that they are not normally visible and their key is needed to view them. Simulation results indicate the efficiency of the proposed method.

In this paper, we described Pearson's correlation coefficient inefficiency for analyzing the relationship between an image and encrypted one. Also, the information index was investigated as a suitable substitute for Pearson correlation coefficient. This weakness is independent of the encryption system of the image encryption; however, two encryption algorithms such as modified AES and W7 stream cipher have been used for laboratory calculations. In addition, by quantitative and qualitative examination of other standards for encryption analyzing of the image, the information index, in comparison with the Pearson correlation coefficient, shows the strengths and weaknesses of the image encryption algorithms better.

In this paper, a new method has been presented for chaos synchronization using a nonlinear controller. In most so-far presented approaches, it is assumed that the mathematical models of the transmitter and reciever are completely the same. Due to the non-identical environmental circumstances in the transmitter and receiver and the influence of temperature on the chaotic system parameters, this assumption is not true. In this paper, a novel approach, in which uncertainties are modeled by a linear diffential equation with unknown constant coefficients, has been presented for estimation of these uncertainties . Since this function satisfies the conditions of the universal approximation theorem, it can estimate nonlinear functions with arbitrary small approximation error. However, since the coefficients are unknown, the parameters of these functions are unknown and should be estimated using the adaptation laws derived from the synchronization analysis. Simulation results verify the effectiveness of the proposed estimator. In comparison with other controllers such as fuzzy sliding mode controllers, the proposed controller response is faster. Moreover, its application in secure communications and cryptography has been studied, as well.

The stream ciphers are one of the most important cryptosystem in cryptography and their applications are very diverse, particularly in defense industries and telecommunications. This crypto system is designed based on a key stream and also the key stream is created using a pseudo random number generator. In this paper, first, a new pseudorandom number generator is designed based on discrete logistic map and independency, uniformity and randomness of the generated numbers by proposed pseudo random number generator are tested by correlation test, goodness of fit test and NIST tests. The tests results illustrate suitable quality of proposed generator for cryptographic applications properly. Next, a new synchronous stream cipher algorithm using the proposed pseudo random number generator is designed and simulated. Finally, the algorithm has been tested using three different methods and is compared with some other cryptography algorithms.