There is a considerable increase in the exchange of data over the Internet and other media types. this Data may contain confidential information that need to be secured from any third party access. Encryption algorithms play a main role for securing these type of data. The encryption algorithms are varied in their performance. This paper evaluates the performance the two encryption algorithms: AES and DES. The performance measure of encryption algorithms will be conducted in terms of processing time, CPU usage and encryption throughput on Windows and Mac platform for a different text size. Experimental results are given to demonstrate the performance of each algorithm.