Cipher

About: Cipher is a research topic. Over the lifetime, 9409 publications have been published within this topic receiving 110309 citations. The topic is also known as: cypher & cryptographic algorithm.

On the existence of low-degree equations for algebraic attacks

Abstract: Algebraic attacks on block ciphers and stream ciphers have gained more and more attention in cryptography The idea is to express a cipher by a system of equations whose solution reveals the secret key The complexity of an algebraic attack is closely related to the degree of the equations Hence, low-degree equations are crucial for algebraic attacks So far, the existence of low-degree equations for simple combiners, combiners with memory and S-boxes was treated independently In this paper, we unify these approaches by reducing them to the same problem: finding low-degree annihilators This enables a systematic treatment and implies a general criterion for the existence of low-degree equations The unification allows to extend former results to all three cases Therefore, we repeat an algorithm for finding a generating set of all low-degree equations Additionally, we introduce a new improved version, adapted to specific keystream generators (eg, for the Bluetooth keystream generator) Finally, we describe for certain cases an upper and a lower bound for the lowest possible degree To the best of our knowledge, the upper bound has only been presented in the context of keystream generators before and the lower bound was not published previously

Method and apparatus for generating a cipher stream

Abstract: A system for encrypting or decrypting a digital message comprising a linear driving subsystem (4) for generating a pseudo random data sequence, a non-linear feedback subsystem (6) for producing a cipher stream from said pseudo, random data sequence, and an encryption processor (26) for encrypting or decrypting a message by combining it with said cipher stream, the non-linear feedback subsystem comprising a non-linear feedback processing means (10) for generating a feedback sequence (12) by applying a non-linear function to at least one value from said pseudo-random data sequence and at least one previous value of the feedback sequence, and a cipher stream generating means (10) for generating said cipher stream by summing products of pairs of values of said pseudo random data sequence together with a value from said feedback sequence, the pairs of values being chosen such that the difference in sequence position as between each member of a pair is different as between each pair.

A new efficient lightweight and secure image cipher scheme

Abstract: The protection of multimedia content has become a key area of research, since very often a user’s privacy and confidentiality can be at risk. Although a large number of image encryption algorithms have recently emerged, only a subset of these algorithms are suitable for real applications. These algorithms however use non-integer operations such as chaotic solutions that introduce a sizeable overhead in terms of latency and resources, in addition to floating-point hardware that is costly to implement. Designing an efficient, lightweight, and secure image encryption algorithm is still a hard challenge; yet, it is crucial to have in order to meet the demands of recent multimedia applications running on energy-limited devices. In this paper, an efficient image encryption scheme based on a dynamic structure is proposed. The structure of the proposed cipher consists of two different lightweight rounds (forward and backward chaining blocks) and a block permutation process. In addition, a key derivation function is proposed to produce a dynamic key based on a secret key and a nonce. This key, according to its configuration, can be changed for each validate time (session) or for each new input image. Then, based on this key, the cipher layers are produced, which are an integer or a binary diffusion matrix and a substitution table S-box, together with a permutation table P-box. The proposed dynamic cipher is designed to provide high robustness against contemporary powerful attacks, and permits reducing the required number of rounds for achieving the lightweight property. Experimental simulations demonstrate the efficiency and robustness levels of the proposed scheme.

DNA-Genetic Encryption Technique

Abstract: In this paper, we propose DNA-Genetic Encryption Technique (D-GET) in order to make the technique more secure and less predictable. In this technique, binaries any type of digital data and convert it to DNA sequencing, reshape, encrypt, crossover, mutate and then reshape. The main stages of D-GET are repeated three times or more. Transmit the encrypted data in text/image format file. In other side, the receiver uses the D-GET to decrypt the received data and reshape it to original format. This Technique also transforms the text into an image and vice versa to improve security and multiple key sequences to increase the degree of diffusion and confusion, which makes resulting cipher data difficult to decipher and makes to realize a perfect secrecy system. Experimental results demonstrate that proposed technique has multilayer protection stages against different attacks and higher level of security based on the multi-stages and genetic operations. Decrypted data are acceptable because of there is absolutely difference between it and secret data.