MODIFYING DES ALGORITHM BY USING DIAGONAL MATRIX BASED ON IRREDUCIBLE POLYNOMIAL

摘要

Risks of computer offenses and requirements for information confidentiality have led to increasing attention on high-security cryptosystems. Conventional encryption methods cannot provide enough security when executed on computer systems. Therefore, modern technology uses the principles of traditional encryption methods and mathematical principles applicable on computers. Data Encryption Standard (DES) must have more robust security than other cryptosystems. However, the process time necessary for cryptanalysis is less than usual. Moreover, as hardware techniques have quickly advanced, the DES may be attacked by several types of cryptanalysis using a parallel process. This study proposes changes in the operation of DES to ensure high security. Such changes include performing matrix multiplication operation instead of Exclusive OR (XOR) operation. Moreover, four keys are used for each round, two of which are derived from the main key and the remaining two are internally generated. The four keys are used in a special sequence with round numbers. The main key is generated from a random string of 64 bytes. Then, the key is expanded and distributed over 16 keys.