Investigation Of Symmetric Encryption Algorithm

Symmetrical encryption and asymmetrical encryption are the two parts of modern encryption.Asymmetrical encryption is also called public key encryption.As for symmetrical encryption,its encryption key and decryption key are the same while asymmetrical encryption has two different keys.AES is short for Advanced Encryption Standard.American National Institute of Standard and Technology assured Rijndael encryption as Advanced Encryption Standard after years of global Encryption competition. That is why AES is called Rijndael sometimes.It has the advantage of simple, High-efficiency and high safety.It is a kind of Symmetrical encryption and can choose three different length keys:128 bites,192 bites and256 bites.Information encryption and Symmetrical encryption are introduced at first. Then I pay more efforts on the realization of 128 bites key AES on VB platform.Optimization works are done next.The operations of encryption and decryption are realized at first.Then I realized the Galois field multiplication.The next work is to realize encryption and decryption with no wrong.Because of the low efficiency of program,some optimization works are done to the Galois field multiplication function.Then, furthermore optimization works are done to the program with a method of creating T tables.The test results prove that these two times of optimization work have made effects.The method of creating T table is better.No wrong is found in the program.My function of realizing Galois field multiplication is complicated, but it is helpful to understand AES and it is the basis of realizing AES。...