A User Centric Security Model for Tamper-Resistant Devices

6.6 Analysis of the Proposed Protocols
The AD will sign the message that includes the transaction certicate of the charge applied
by the AD. The payment details (pd) includes the charge method (chm), charge value (chv)
and payment method (pm). Finally, the AD also generate the SID (SID ′ AD−SC) and SC i ′
to be used in the subsequent session.
After the SC receives the ActApp, it will activate the application and notify the cardholder
about the successful outcome of the application installation, and any charge that was
incurred by the AD. The charging mechanism for the individual transactions is at the sole
discretion of the AD. This message also acts as proof of the transaction.
6.6 Analysis of the Proposed Protocols
In this section, we discuss the proposed protocols in terms of informal, and formal mechanical
analysis using CasperFDR. Later, we detail the test implementations and experimental
results.
6.6.1 Informal Analysis of the Proposed Protocols
In this section, we informally discuss the requirements for the STCPs namely STCP SP ,
STCP SC and STCP ACA .
6.6.1.1 One to Twelve
In this section, we consistently refer to the protocol requirements and goals in section 6.2.3
with their respective numbers as listed in the same section. Therefore, from here onward,
any reference to a goal or requirement number refers to the listed item in section 6.2.3.
During the STCP protocols, the message AU X where X = SC, SP and U, authenticates
communicating entities satisfying the SOG-1. To satisfy the SOG-2, all communicating
entities exchange cryptographic certicates that also facilitate in entity authentication process.
The proposed STCPs satisfy requirements SOG35 and SOG12 by rst requiring the SP to
generate the Die-Hellman exponentials as it is computationally more powerful than the
smart card. If the smart card generates the exponential before the SP then it can choose
a weak key; however, as smart cards are computationally restricted devices they cannot
perform such tasks. After generation of session keys, communicating entities use them to
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