The number of VoIP users in Indonesia is very low, although the cost offered by VoIP is smaller than using pulsed phone. One of the reason is security provided by the VoIP service provider is still lacking. VoIP users have not received yet the security service to ensure the security of communications. This study tries to secure communications between VoIP users using encryption module that is integrated with VoIP client Sipdroid running on Android Smartphone. It is possible for VoIP users because VoIP client that can only be accessed by VoIP users. The result obtained after integration with encryption module using three encryotion schemes, they are AES, DES, and RC4. Sipdroid able to resist passive attack from tapping information (eavesdropping) during the communication session. And the result of QoS measurements is an increase delay of 0.01 ms and no significant change in the throughput and the packet loss, for throughput generated about 78 kbps, and for the average packet loss is 0.8%. However there is a noise that follows the communication on Sipdroid integrated with the encryption module due to the wave skew from the increase time during the encryption process.