Cryptili is a lightweight Android app that allows you to encrypt/decrypt messages and send them through a different app.

It uses a sophisticated subtitution algorithm (Vigenere) to which you need to provide a key in order to encrypt your messages.

Other features:

-You can either keep track of your history and save messages that you have encrypted/decrypted or you can use Cryptili without saving your history. -You can select a text in another app and choose Cryptili in "share" to encrypt/decrypt the selected text. -There is a FAQ section in the menu.