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.
Authentication is relatively straightforward with a powerful enough smartcard.
Price information can be shown on a secure display in the obvious way. Authenticationand delegation with smart-cards. Technical Report 67, DEC Systems Research Center, October 1990. Doc 106 Zero Knowledge Proofs of Identity - Feige, Fiat et al. A Calculus for Access Control in Distributed Systems - Abadi, Burrows et al.