A User Centric Security Model for Tamper-Resistant Devices

6.7 Summary
For the STCP ACA , we need to provide the digest of the downloaded application. To do this
we emulated the performance measure by monitoring the time it took to generate hash on
a 256 bytes array. The hash generation on the 256 bytes took 31 milliseconds on the test
smart cards. The performance measures of hash generation on the test smart cards with
dierent sizes of the download application are shown in gure 6.2
Time (Miliseconds)
11000
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
1 17 33 49 65 81 97 113 129 145 161 177 193 209 225 241
Input Data (Kilobytes)
Figure 6.2: Performance measurements of hash generation on test smart cards
The STCP ACA can be divided in to three distinct phases that are listed in the table 6.4
along with the breakdown of the performance measure. The breakdown provides a rough
guide how much extra time these protocols will take if the protocols STCP SC and STCP SP
are extended to provide SOG-18 and SOG-19.
Table 6.4: Breakdown of performance measurement (milliseconds) of the STCP ACA
Phases
Measures
STCP ACA
C1 C2
AKA Phase (STCP ACA -1 4) Average 3182 3334
Contract Phase (STCP ACA -5 6) Average 1253 1294
Charge Phase (STCP ACA -7 8) Average 1407 1470
Total (STCP ACA -1 8) Average 5843 6098
The performance measures are only for the reference of our implementation, as the actual
performance will vary depending the attestation process, the application size, and the
communication speed (i.e. Internet bandwidth).
6.7 Summary
In this chapter, we discussed Secure Channel Protocols (SCPs) and their role in the UCTD.
In addition, we provided the rationale behind proposing new SCPs. This was followed by
an account of the related work in the eld. We discussed security and operational goals
for the proposed protocols. We then proposed three protocols that satisfy varying levels
of security and operational goals, along with the user's and SP's requirements. These
protocols were then analysed informally for a limited set of security goals and compared
with a set of selected protocols. We subjected the proposed protocols to mechanical formal
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