Abstract. Full-text article available at: http://dx.doi.org/10.17781/P002657A secure communication over the web is being provided by encryption algorithms and so they still play a serious role in any security system. However, a substantial amount of your time and resources like memory, CPU time, and computation time to encrypt and decrypt data are being consumed by these algorithms. Therefore, this study empirically investigated the efficiency of secret key encryption algorithms with similar key length and block size to identify the best algorithm which provides optimum performance. So, diverse experiments have been performed to evaluate the performance of IDEA, Blowfish, and CAST5 symmetric encryption algorithms in terms of throughput, encoding time, and decoding time over variable text files and modes of operation. The results of the experiments show that Blowfish is the most competent data encoding algorithm as far as the used parameters are concerned