Todays, short messages service (SMS) still represents the foremost used mobile electronic messaging service. SMS messages are employed in many various applications, even in cases wherever safety features, like authentication and confidentiality between the communications, should be ensured. Unfortunately, SMS technology doesn’t give inbuilt support for any safety features. Hence the secured communication on SMS could be a big challenge. In this work, we use the communication between peers is secured by using public-key cryptography. It includes SMS network architecture as well as cryptographic protocols as a theoretical background and it also deals with design, implementation and confidentiality assessment of RC4 stream cipher for SMS data confidentiality on mobile networks. To secure the message, the receiver needs to put a password. In the paper, we compare the RC4 and RSA algorithm for data confidentiality on SMS.