Abstract: A method implemented on a computing device provides for identifying the device and/or a user to an application on the device. The method comprises receiving a function call for a public identifier, responding to the function call, performing a hash operation and returning the public identifier. Responding to the function call comprises requesting a publisher ID from a first memory location within the device and requesting a private ID from a second memory location. Performing a hash operation on the publisher ID and the private ID creates the public identifier. The public identifier is then returned to the application. A method of allowing a developer to test an application on a mobile device or emulator is also described. A mobile device programmed to return a public identifier to an application is also described.