A User Centric Security Model for Tamper-Resistant Devices

7.3 UCTD Firewall
Smart Card A
Server
Application
Sharing
Request
Smart Card Runtime Environment
Fake Client
Application
Message transfer
by the malicious user
Fake Server
Application
Sharing
Request
Smart Card Runtime Environment
Smart Card B
Client
Application
Figure 7.7: Application masquerading and relay attack scenario
SOG-20 Application Masquerading. In this scenario, a malicious application can masquerade
as a server or client application. For example, in Java Card when a client
application sends a request for application sharing it generates the request that contains
the server application's AID. Now if a malicious application is masquerading
as a server application, it only has to inform the rewall that it accepts the application
sharing request without validating that it has the knowledge of the shared
secret. Thus the client application thinks that it is accessing the shared resource
of the server application, whereas in fact it is communicating with a malicious
application. Now the fake server application can resend the application sharing
request message to a genuine server application on another smart card and gain
access to shared resources; this scenario is illustrated in gure 7.7.
SOG-21 Dierent User's Applications. Consider a scenario in which we have two users
and two applications. One is a malicious user M u while the other is an authorised
user A u . The two applications are App A (server application) and App B (client
application) that have a client-server relationship. Both users are authorised to
download application App A , however M u is not authorised to download application
App B . Now at some point, the M u obtains the App B 's credentials for the A u and
manages to download App B onto his or her smart card. The application sharing
between the M u 's App A and the A u 's App B can be established. This can lead to
some nancial benets for the M u to which he or she is not entitled.
Request for App A
Credentials (M u)
SP of App A SP of App B
App A
Credentials (M u)
M Request for App App B
B
u
Credentials (A u) Credentials (A u)
Server
Application
(App A-M u)
Smart Card of M u
Sharing
Smart Card Runtime Environment
Client
Application
(App B-A u)
Figure 7.8: Application sharing among dierent user's applications
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