Authentication and Delegation with Smart-cards

The authentication of users in distributed systems poses special problems because users lack the ability to encrypt and decrypt. The same problems arise when users wish to delegate some of their authority to nodes, after mutual authentication. In most systems today, the user is forced to trust the node he wants to use. In a more satisfactory design, the user carries a smart-card with suucient computing power to assist him; the card provides encryption and decryption capabilities for authentication and delegation. Authentication is relatively straightforward with a powerful enough smart-card. However, for practical reasons, protocols that place few demands on smart-cards should be considered. These protocols are subtle, as they rely on fairly complex trust relations between the principals in the system (users, hosts, services). In this paper, we discuss a range of public-key smart-card protocols, and analyze their assumptions and the guarantees they ooer.