A User Centric Security Model for Tamper-Resistant Devices

7.3 UCTD Firewall
and asynchronous application sharing respectively. Synchronous application sharing enables
two applications to communicate in real-time, and they can be considered as real-time
distributed systems. In case of the asynchronous application sharing the communication
between applications can occur when both are available (live in the network). Both schemes
have benets and drawbacks; therefore, it is at the sole discretion of the individual set of
client-server applications to decide which mode they will employ. For further explanation
and to provide a contrast between these two mechanisms consider the following examples.
Consider two applications, one of them provides access to certain internet services, and
the second application is an internet identity [193] that acts like a Single-Sign-On (SSO).
Every time a user logs on to the Internet services through the rst application, a connection
has to be established with the second application to provide the internet identity for user
authentication and authorisation. This access to the SSO application has to take place
when the rst application connects with the internet services. Such an access is termed as
synchronous access in the UCTD and is based on the Java Card architecture [186]. Such
an access can be based on the Java Card Remote Method Invocation (RMI) [28].
For asynchronous access, we also take an example of two applications. One application
provides electronic wallet functionality, and the second is a loyalty application. Every time
the electronic wallet application is used, the cardholder earns loyalty points. The loyalty
application does not have to be live. The electronic wallet application batches the loyalty
point update task and when the loyalty application becomes live, it can proceed with
updating it. For this purpose, a simple mechanism deployed by the Multos application
sharing would suce. The electronic wallet application batches the APDUs to update the
loyalty application. When the loyalty application comes online, all batched APDUs can
be communicated to it.
In the next section, we describe the goals and requirements of the proposed protocols to
establish application and platform binding, before we look into the details of Application
Binding Protocol Local (ABPL) that focuses on the application binding between two
applications on the same UCTD. Later, we discuss the Platform Binding Protocol (PBP),
and Application Binding Protocol Distributed (ABPD) that are proposed to support
the CDAM.
7.3.7 Minimum Goals and Requirements for the Proposed Protocols
The goals and requirements for the proposed protocols that facilitate the establishment of
application and platform binding are listed below. This list is an extension to the list in
section 6.2.3, with the exception of requirements SOG-17 to SOG-19. Later, we will revisit
these goals for the protocol comparison in section 7.7.2.
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