This paper addresses to structures and properties of the cryptographic information protection algorithm model based on NPNs and constructed on an SPnetwork. The main task of the research is to increase the cryptostrength of the algorithm. In the paper, the transformation resulting in the improvement of the cryptographic strength of the algorithm is described in detail. The proposed model is based on an SP-network. The reasons for using the SP-network in this model are the conversion properties used in these networks. In the encryption process, transformations based on S-boxes and P-boxes are used. It is known that these transformations can withstand cryptanalysis. In addition, in the proposed model, transformations that satisfy the requirements of the "avalanche e ect" are used. As a result of this work, a computer program that implements an encryption algorithm model based on the SP-network has been developed.
This paper addresses to a variation (modification) of a symmetric block encryption-decryption algorithm based on nonpositional polynomial notations (NPNs). The proposed encryption model includes two stages. The first stage is that a plaintext is split into bit blocks of a given length. Each plaintext block then undergoes an initial transformation, where a pseudorandom sequence (PRS or key sequence) is added bit by bit to the block through XOR operation. The key sequence is generated with a designed PRS generator. In the second stage, an encryption-decryption algorithm based on NPNs is applied to the transformed bit sequence. A computational model has been developed and implemented to test statistical properties of the sequences enciphered under the proposed modification of the encryption-decryption algorithm.
Cryptographic technologies that have become widespread in the world are inex- tricably linked to the issues of secure storage, use of keys, and key exchange. Often, insecure key management reduces the quality of even exceptionally good systems, since the security of the algorithm is concentrated mainly in the key. This paper proposes a key management model in cryptographic systems. The model is based on creating a unified key database for all users. This database is filled with keys of a certain length, which are generated using a pseudo-random sequence generation algorithm.
Lightweight encryption algorithms are considered a relatively new direction in the development of private key cryptography. This need arose as a result of the emergence of a large number of devices with little computing power and memory. Therefore, it became necessary to develop algorithms that can provide a sufficient level of security, with minimal use of resources. The paper presents a new lightweight LBC encryption algorithm. LBC is a 64–bit symmetric block algorithm. It supports 80 bit secret key. The number of rounds is 20. The algorithm has a Feistel network structure. The developed lightweight algorithm has a simple implementation scheme, and the transformations used in this algorithm have good cryptographic properties. This was verified by studying the cryptographic properties of the algorithm using the "avalanche effect" and statistical tests. The avalanche property was checked for each round when each bit of the source text was changed. Based on the work carried out, it was found that the proposed encryption algorithm is effective to ensure a good avalanche effect and the binary sequence obtained after encryption is close to random. Its security against linear and differential cryptanalysis is also evaluated. The results of the research revealed good cryptographic properties of this algorithm. The algorithm will be used for devices with small hardware resources, in information and communication systems where confidential information circulates, and it is also extremely necessary to exchange information in a protected form in an operationally acceptable time
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