participants: users, smart cards, card readers, servers and a key server.
These components communicate over a network which is shared with many
unrelated activities as depicted in Figure 1.

\include case2fig2.eps here.



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can proceed.

\include case2fig1.eps here

The network activity is depicted in Figure 2.  Note that most activity takes
place at the physical link between the smart card and the card reader.  There
are three transactions which take place over the network.  All of these are
encrypted and signed making them secure against alteration and packet
sniffing.