RVGAC: A Round-Variable Authentication Code Based on a Hybrid Rijndael–Feistel Block Cipher for Network Security

Abstract

The increasing frequency and sophistication of cyberattacks have made data confidentiality and integrity critical challenges in modern networked systems. Encryption algorithms, particularly symmetric-key block ciphers, form the foundation of contemporary cybersecurity infrastructures. Although well-established block ciphers such as AES provide strong security guarantees, their fixed round structures and static diffusion paths may introduce structural regularities when deployed in large-scale or long-term network environments.This paper proposes a novel symmetric-key block cipher, referred to as the Round Variable Generation Authentication Code (RVGAC), which integrates Feistel-based round swapping with Rijndael-inspired nonlinear substitution and linear diffusion mechanisms. The proposed design introduces controlled round-variable behavior, increasing cryptographic uncertainty and reducing exploitable statistical correlations. RVGAC achieves confusion through nonlinear FS-Boxes and S-Boxes, and diffusion through AddRoundKey, P-Vector permutation, MixColumns, and Feistel swapping.The security and randomness of the generated ciphertext sequences are evaluated using the NIST Statistical Test Suite and Strict Avalanche Criterion (SAC) analysis. Experimental results demonstrate strong statistical randomness and effective diffusion across multiple data types. These findings indicate that RVGAC is a suitable and robust block cipher for modern network security applications.