Security is the most challenging aspects in the internet and network applications. Internet and networks applications are growing very fast, so the importance and the value of the exchanged data over the internet or other media types are increasing. Data confidentiality and authentication are normally provided using cryptographic techniques. Cryptography is either based on symmetric keys or asymmetric keys. This paper provides a fair comparison between three most common symmetric key cryptography algorithms: DES, AES, and RC5. Since main concern here is the performance of algorithms under different settings, the presented comparison takes into consideration the behavior and the performance of the algorithm when different data loads are used. Based on implementation and study, runtime comparison between the symmetric cryptosystems has been made.