CIFRADOR DE BLOQUES, UTILIZANDO LA TRANSFORMACIÓN CAÓTICA UNIDIMENSIONAL DE LA TENT

Abstract

This thesis shows the design, construction and evaluation of a ciphering block algorithm based on a Tent chaotic transformation function as a dynamic chaotic system. Block and encryption key are 64 bits size, with sub-blocks of 8 bits. The non-linear function used in the non-balanced Feistel network has as its basic function the Tent chaotic transformation. During the evaluation process of this cipher, when analyzing the bifurcation diagram it can be observed that this is not completely dense once it is scaled and discretized in the universe of Extended ASCII, it was decided to design, construct and evaluate another block cipher to keep the 64 bits length in the blocks and the encryption key, but now divided into 4 sub-blocks of 16 bits. Afterwards, the entropy of the input file (clear text) is calculated and compared with the entropy of the output file (ciphered text) as a diffusion measure during the ciphering process, according to Chapter IV. It also compares the performance of the proposed algorithm with other ciphering block algorithms using chaotic and sine logistic transformation, as well as other algorithms that have good market acceptance [1] (AES, DES, TRIPLE DES, BLOWFISH, IDEA Y SKIPJACK), based on the security criteria proposed by Claude E. Shannon through the estimation of Mutual Information and the Statistical Distribution of the cryptosystem using NIST randomness statistic tests [2]. Finally, the results of the proposed algorithms are shown, in these results it can be seen that the Tent chaotic transformation offers better behavior conditions in a block cryptosystem that when using other chaotic transformations, such as logistics and sine, even when using commercial cryptosystems, as reported on the results of entropy.