CeTrivium: A Stream Cipher Based on Cellular Automata for Securing Real-Time Multimedia Transmission.

Due to their significant correlation and redundancy, conventional block cipher cryptosystems are not efficient in encrypting multimedia data. Stream ciphers based on Cellular Automata (CA) can provide a more effective solution. The CA have recently gained recognition as a robust cryptographic primitive, being used as pseudorandom number generators in hash functions, block ciphers and stream ciphers. CA have the ability to perform parallel transformations, resulting in high throughput performance. Additionally, they exhibit a natural tendency to resist fault attacks. Few stream cipher schemes based on CA have been proposed in the literature. Though, their encryption/decryption throughput is relatively low, which makes them unsuitable for multimedia communication. Trivium and Grain are efficient stream ciphers that were selected as finalists in the eSTREAM project, but they have proven to be vulnerable to differential fault attacks. This work introduces a novel and scalable stream cipher named CeTrivium, whose design is based on CA. CeTrivium is a 5-neighborhood CA-based stream cipher inspired by the designs of Trivium and Grain. It is constructed using three building blocks: the Trivium (Tr) block, the Nonlinear-CA (NCA) block, and the Nonlinear Mixing (NM) block. The NCA block is a 64-bit nonlinear hybrid 5-neighborhood CA, while the Tr block has the same structure as the Trivium stream cipher. The NM block is a nonlinear, balanced, and reversible Boolean function that mixes the outputs of the Tr and NCA blocks to produce a keystream. Cryptanalysis of CeTrivium has indicated that it can resist various attacks, including correlation, algebraic, fault, cube, Meier and Staffelbach, and side channel attacks. Moreover, the scheme is evaluated using histogram and spectrogram analysis, as well as several different measurements, including the correlation coefficient, number of samples change rate, signal-to-noise ratio, entropy, and peak signal-to-noise ratio. The performance of CeTrivium is evaluated and compared with other state-of-the-art techniques. CeTrivium outperforms them in terms of encryption throughput while maintaining high security. CeTrivium has high encryption and decryption speeds, is scalable, and resists various attacks, making it suitable for multimedia communication.