Encryption performance and security of certain wide block ciphers

Abstract

In a context of enhancing the performance of block encryption algorithms there are two well-known approaches. The first one relates to the construction of block cipher modes of operation. This approach is effective, but it requires a specific proof of security. The second approach deals with the construction of a cryptographic algorithm itself. In this paper, we introduce a novel family of schemes with a block size ranging from 256 up to 1056 bits. We call these algorithms Wide Block Ciphers (WBCs). The round transformation of the considered WBCs is based on a shift register with several feedbacks (the design is similar to the generalized Feistel networks). For the encryption transformation, i.e. the composition of round transformations, we study the properties of confusion, diffusion and mixing by methods of the Matrix-Graph Approach. We present a technique for evaluating these properties, which allows us to choose the algorithm parameters (block size, number of feedbacks, feedback locations) and propose the schemes reaching rational compromise between the encryption performance and the security level. The considered algorithms show better performance than other similar algorithms implemented by the original Feistel network with the same number of rounds. Without loss of generality, we focus on 256-3 version (256-bit block and three feedbacks). Developers can use the proposed schemes as building blocks of the algorithms for ensuring information confidentiality and integrity.