A User Centric Security Model for Tamper-Resistant Devices

6.2 Secure Channel Protocols
6.2 Secure Channel Protocols
In this section we explore the rationale behind SCPs for the UCTD, and then discuss the
relevant work in the eld of SCPs. This discussion forms the basis for work later in this
thesis.
6.2.1 Rationale
By denition, an SCP provides either (or both) entity authentication or key exchange between
communicating parties, referred to as end points. The SCP preserves the condentiality
and integrity of the messages communicated on the channel but does not necessarily
assure the same security at the end points after the messages are received. Despite this,
there can be implicit condence in the integrity and security of the end points in the ICOM
as articulated by ETSI TS 102 412 [164, section 4.5.2]. This states that the smart cards
are a secure end point under the assumption that it is a tamper-resistant device.
This implicit assumption is valid for the traditional smart card environment because smart
cards are issued by a trusted card issuer. This became the fundamental assumption in
most of the smart card-based SCPs. For the ICOM, this assumption makes sense as the
strict control of application installation on a smart card will eectively restrict the SCP to
only execute with an entity that: a) has prior authorisation from the card issuer, or b) is
initiated by an on-card authorised entity (e.g. installed application).
In the ICOM, there is a centralised authority that controls issued smart cards and their
application management, enabling an implicit assurance attainable for the smart card
security and reliability. However, in the UCOM, there is no such authority, hence the
assumption of implicit assurance is no longer valid. The UCTD is required to provide an
explicit assurance of its integrity and security to the requesting SP to satisfy requirements
GR2, CR1, SCR1, SCR6, and SPR15 (section 3.5).
A trusted channel is a secure channel that is cryptographically bound to the current state
of the communicating parties [165]. This state can be a hardware and/or software conguration,
and ideally, it will require a trustworthy component to validate that it is the same
as claimed. Such a component is in most instances a Trusted Platform Module (TPM) [18]
as demonstrated by Zhou and Zhang [166], and Armknecht et al. [167].
The SP will probably not have any prior trust relationship with a smart card in the UCTD
environment (an exception might exist in the CASC framework when the SP is a syndicated
member of the administrative authority). Therefore, the traditional smart card SCPs will
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