Abstract: A method of producing a security code by means of a programmable user device is described. The security code produced represents in itself both the user and the user device. In one embodiment, a service provider code representing a service provider by whom the user is registered with his/her user name forms an addition to the basis, on which the security code is calculated. The security code is useful for several security applications, such as for user authentication, and for local storage of information, as well as for signing and encryption/decryption of information to be exchanged between the user and a service provider, or vice versa.