Authentication and access control are normally considered as separate security concepts that have separate goals and are supported by separate security mechanisms. In most operating systems, however, access control is exclusively based on the identity of the requesting principal, e.g., an access control mechanism based on access control lists simply verifies that the authenticated identity of the requesting principal is on the list of authorized users.
In this paper we propose a human-to-human delegation mechanism for nomadic users, which exploits the amalgamation of authentication and access control in most operating systems, by delegating privileges at the identity level. The complexity of classic delegation models, especially if they strictly follow the principle of least privileges, often leads to a poor usability, which motivates a user to circumvent the default delegation mechanism. On the other hand, the identity delegation makes good use of trust relationships among users of a particular environment and offers the possibility of improved usability. Although identity delegation might violate the principle of least privileges, in practice it could increase the over all security of a nomadic environment where users need to delegate their duties frequently. The proposed mechanism is independent of the access control and the delegation event is only logged at the authentication level. Due to its improved usability, the motivation to share authentication tokens is reduced.