A User Centric Security Model for Tamper-Resistant Devices

8.3 Runtime Protection Mechanism
4. Unknown error: In this scenario, an adversary generates a fault but has no location
and timing control.
From the above list of fault models, the rst model adversary can be considered the most
powerful. However, for a smart card environment the second scenario (i.e. precise byte
error) is the most realistic one. Due to the advances in the smart card hardware and
counter-measures against fault attacks (i.e. especially for cryptographic algorithms) it is
dicult to have total control of timing and locations of bits to ip [216]. Furthermore, fault
attacks require knowledge of the underlying platform and application execution pattern
[191]. This is possible to achieve by side-channel analysis [197].
8.3 Runtime Protection Mechanism
In this section, we provide the motivation behind the runtime protection mechanism, which
is followed by the description of the attacker's capability. Subsequently, we discuss the
runtime protection mechanism, how it provides a secure and reliable framework for the
UCTD runtime environment.
8.3.1 Motivation
During an application's lifetime, it mostly interacts with the runtime environment and
the application's security is dependent on the security of the runtime environment. This
means that an insecure runtime environment can in fact make a well-designed application
insecure. Although, as discussed in section 4.4, a UCTD is required to be certied by a
third party evaluation (e.g. CC evaluation); however, we still consider that the runtime environment
should not rely only on static security mechanisms including security evaluation
and bytecode verications (both o- and on-card).
As discussed in section 8.2.2, a smart card runtime environment is increasingly facing
the convergence of various attack techniques (e.g. fault and logical attacks). Physical
protection mechanisms regarding fault attacks are proposed [221]; however, we consider
that the necessary software protection for the runtime environment cannot be understated.
The software protection can augment the hardware mechanism to protect against the
combined attacks, as a similar approach has yielded successful results in the secure design
of cryptographic algorithms for smart cards [222][224]. In this chapter, we will only focus
on the software protection mechanism, without detailing the hardware-based protection.
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