Ciphering algorithms play a main role in this digital era, especially when data are transferred via internet. Many algorithms has been developed and used to encrypt and decrypt data for secure storing or transmission. At present, both synchronous and asynchronous encryptions are used to achieve the high security and to speed up the encryption time and process. Advanced Encryption Standard (AES) plays a prominent role among the synchronous encryption algorithms. It is also known as Rijndael Algorithm. Because of high performance of AES algorithm, it has been chosen as a standard among symmetric cipher algorithms. In this paper, we would like to propose a symmetric encryption algorithm. Modification is based on AES and we add an additional or second key. Another modification is also done at SubBytes step by adding the transportation operation in the original SubBytes operation. To analyze the performance of the modified proposed algorithm, Java language is used to implement the algorithm and then the performance is analyzed. After analyzing and verifying the experimental results, the proposed revised algorithm also shows good performance and high security from the cryptographic point of view. Based on the results of comparison between modified AES and original AES algorithm, our proposed algorithm can be used as a symmetric encryption algorithm, especially for the applications that share sensitive data files via insecure network.
