Um estudo sobre criptografia simétrica baseada em autômatos celulares híbridos

Abstract

Due to the increasing number of computational systems connected to the Internet, there is a higher demand for faster and more secure ways to allow communication between such systems. Confidential information is often exchanged between personal devices and/or servers, and it must be protected. Cryptographic methods and techniques are used to provide data secrecy between parties and allow the existence of internet banking systems, online stock market operations, secure online personal identification, and so on. There are classical cryptographic methods, such as AES (Advanced Encryption Standard)and DES (Data Encryption Standard), which have been the industry standards for many years. While DES has been mostly deprecated, AES is still considered a secure algorithm. However, AES has some shortcomings, mainly when dealing with image data encryption and regarding multithread optimization. An alternative is developing new cryptographic methods based on systems that display a greater potential for parallelism in current-age computers and specialized hardware. Some of these novel possibilities involve Cellular Automata (CA) due to it being an inherently parallel model. A novel algorithm called VHCA (Very Heterogeneous Cellular Automata) was developed in the scope of this thesis. In VHCA, CA rules extracted from a secret key are repeatedly applied to cells in lattices whose values were initialized with chunks of the plaintext. These successive CA evolutions will result in configurations (states) matching the corresponding chunks of the ciphertext. Initial experiments point to VHCA being a promising solution in the search for new cryptographic models.