The development of existing telecommunication technology at this time able to create various kinds of hardware that can be used to send or receive information quickly and easily. The growing development of existing telecommunication technology results in the possibility of existing or stored information is easy to read, one of which is SMS messages. Unfortunately, an operator can view or read the message content. If the content of the message can be read by others, then the message sent is not safe because the contents of messages that should be confidential to be viewed and read by others .. To solve the problem it will be made android applications Whatmas using cryptography algorithm RSA (Rivest Shamir Adleman) for encryption and decryption of text messages. This app is built in Android Studio, using JAVA programming languages, and SQLite databases. Whatmas app uses the minimum SDK of android jelly bean
