A User Centric Security Model for Tamper-Resistant Devices

4.4 Security Assurance and Validation Mechanism
the individual smart cards that have the same validity as the associated PAC.
4.4.2.2 Application Evaluation Phase.
An SP would create an ST according to its security requirements and get it evaluated
by the CLEF. If the SP's application is approved, the CB would issue a cryptographically
signed Application Assurance Certicate (AAC) that would contain the EAL level achieved
by the SP's application and the hash of its immutable application code.
The structure of the AAC is similar to the PAC, except for few changes. Details of data
elds included in the AAC are: the SP's ID, the evaluator's (CLEF) ID, reference to the
evaluation target documents (PPs and ST), a digest of immutable application code, the
SP's signature key, and the certicate's validity period.
The certicate chain traversal and verication of the individual certicates in the chain
are comparatively easy for the SPs as they have more computational power than a smart
card and independent access to an external network (i.e. the internet). To perform such
tasks would no doubt be challenging for a smart card; therefore, it would request the SP
to provide the certicate hierarchy that leads back either to the smart card manufacturer
or the third party evaluator of the smart card (i.e. to an entity that is considered trusted
by the smart card). In this way, the smart card can easily verify the certicate as the root
of the certicate chain provided the SP's certicate chain has entities (certicate issuers)
that the smart card trusts.
4.4.3 Validation Phase
This phase deals with the process that provides a dynamic and remote attestation of the
current state of the smart card or applications. The attestation mechanism combines the
self-test manager and attestation handler of the TEM to provide the state validation of
the UCTD. For validation of applications the TEM attestation handler only generates the
hash of the application in question, but the attestation mechanism for UCTD validation
has two modes of operation: oine and online. In the oine mode, the validation process
is independent of the card manufacturer and the smart card provides a security validation
message to the requesting entity. In the online mode the card manufacturer provides the
security validation message (i.e. a signed message from the card manufacturer) to the
requesting entity.
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