In the past few weeks I put together an android application which is similar to Crystal in my old blog post. This application allows the user to store text data on an android device by encrypting it. Crystal v 1.0 for android uses java security libraries available on android sdk. Crystal allows you to create a master password for your data files. Once you set your master password, you can write files using crystal and save them in encrypted form and read them later with your master password.
Crystal v 1.0 for android apk file is here . You will need a third party application to install it on your android phone. (Until I get my android market account set properly !)
More screen shots and how to use crystal is here
1) Your master password is immutable.
2) Crystal Selects the location for files on your device automatically.
3) AES is the only algorithm supported in the current version.
How it works
Crystal uses java security on android to create a master keystore on your device. This key store holds your key which is used to encrypt/decrypt your data files. The keystore has a password which is the master password. You set this password while using the application and it automatically generates a symmetric key and stores it in your keystore. The master password is never stored anywhere on your device. Your key is also safe as long as you keep your master password.