Methods and apparatus, including computer program products, for storing data for use on a mobile device on a removable storage medium. To access the data, credentials are received from a user of a mobile device. An encrypted set of data is transferred to the mobile device from the removable storage medium, which is in communication with the mobile device, in response to instructions from an application associated with the data. The encrypted set of data is decrypted based on the credentials, and the decrypted set of data is automatically erased from the mobile device. The removable storage medium can be removed from the mobile device, and the encrypted data can be synchronized with a central database using a proxy device.