A User Centric Security Model for Tamper-Resistant Devices

7.7 Analysis of the Proposed Protocols
• SOG-20: A malicious application can be installed with either a server or a client application's
AID. However, the ABP does not allow a malicious application to masquerade
as a server or client application because to prove the identity of an application, the ABP
does not rely on the AIDs. It has a dynamic mechanism with bi-directional exchanges
of messages that ascertain the entity and check its credentials (based on cryptographic
certicate and signature generation/verication). Therefore, it might be dicult for a
masquerading application to match the cryptographic hash (generated by the TEM) and
have the signature key of the genuine application.
A malicious user can relay the binding request messages, but when these messages are
forwarded to the TEM to generate the hash of the client and server application, a malicious
application's hash will not match the certied hash of the client and server application.
This is equivalent to violating the 2nd pre-image property of the hash functions [146].
In addition, IMA messages include random numbers that eectively prevent any replay
attacks.
The server and client applications authenticate one another. The authentication is achieved
through signing the messages along with communicating the application's certicate. The
authentication gives an assurance to each of the participant applications that the other
application is genuine (eectively avoiding masquerading).
• SOG-21: The application certicate contains details of the user to whom the application
was issued. Therefore, if a client application tries to establish an application sharing with
a server application, but their customer credential does not match, the request is denied.
This avoids application sharing between two applications from dierent users.
7.7.2 Revisiting the Requirements and Goals
In this section, we only discuss SOG-20 and SOG-21. For SOG-1 to SOG19 refer to sections
6.6.1 and 6.6.3.
All selected protocols for comparison can be adapted to support SOG-20 in the way discussed
in section 7.7.1. Furthermore, the PBP does not support both SOG-19 and SOG-20
as it is a protocol designed for establishing a binding relationship between UCTDs, not
their applications, whereas, SOG-19 and SOG-20 focus on application binding rather than
platform binding. A point to note is that ABPL does not support a number of the SOGs,
for the reason that ABPL key generation is based on a symmetric cryptosystem. The
ABPL do uses signature algorithms for entity authentication, and they do not play any
role in key generation. Furthermore, the key generation in the ABPL is performed mainly
by the TEM and server application, without any input from other communicating entities.
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