A Dynamic 3D S-Box based on Cylindrical Coordinate System for Blowfish Algorithm

Abstract

Blowfish Algorithm (BA) is a symmetric block cipher that uses Feistel network to iterate simple encryption and decryption functions. The BA key varies from 32 to 448 bits to ensure a high level of security. However, S-boxes in the BA have a high percentage of memory. A new cryptography algorithm based on BA is designed to overcome this problem. This algorithm adapts a new function (F-function) into a Cylindrical Coordinate System (CCS). The F-function is known as Cylindrical Coordinate System with Dynamic Permutation Box (CCSDPB). The study involved three phases: design, implementation, and verification. In the first phase, dynamic 3D S-box, dynamic P-box, and F-function were designed. The second phase involved performing key expansion, data encryption, and data decryption. Verification includes evaluating the output of the new design using the National Institute of Standard and Technology (NIST) randomness statistical test and cryptanalysis. Results of the statistical tests show that the new design is suitable with any data stream, including a long string of identical bytes. The combination of a dynamic permutation box with a dynamic 3D S-box is an effective approach that strengthens the design resistance against attacks such as differential, linear, and short attacks, as well as and increase the randomness of outputs.