Short Message Service (sms) security solution for mobile devices

B. FAILED 
APPROACHES 
Figure 23 illustrates the logic associated with the original intended 
program flow. However, the program flow below cannot be implemented due to 
certain software limitations, which will be discussed in the following Sections. 
Start
Write time taken and 
power consumption 
data to log file
Read Clear 
Text Input
Set Number 
of Iterations
Check battery 
level
Start timer
Start 
encryption
End of loop?
End
No
Yes
Check battery 
level
Stop timer
Figure 23. Flowchart for Performance Measurement (Original 
Approach) 
1. Power 
Measurement 
Resolution 
The battery power level was accessed through the 
SystemState.PowerBatteryStre
ngth
property using the State and Notification API 
(SNAPI). However, the returned value was expressed as power levels in 5 
distinct bands: Very Low (0-20%), Low (21%-40%), Medium (41%-60%), High 
(61%-80%), Very High (81-100%). This resolution was clearly insufficient and 
another approach was required. 

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2. 
Failure in SNAPI Notification Service 
Another approach was adopted to make use of the notification feature of 
the SNAPI to detect the changes as the battery levels as it changes from one 
band to another. By noting the number of iterations of encryption that causes 
battery level to change by a 20 per cent range, the consumption figure for each 
iteration of encryption can be approximated. The program was coded according 
to the flow chart in Figure 25.
Start
Write start & stop 
loop counters & 
timing data to log file
Read Clear 
Text Input
Start Battery 
Power Notification 
Service
Start 
encryption
Notification 
triggered ?
End
No
Yes
Set Stop flag
Note loop 
counter & time
Start loop 
counter
Reset Stop 
flag
Stop flag 
set?
No
Yes
Figure 24. Flowchart for Performance Measurement (Second 
Approach) 
However, this approached also failed because the Notification Service in 
the SNAPI failed to trap the power changes while the application was 
executing the loop. As the result, the program executed till the end of the loop 
without any interruptions and all the system notifications appear after the loop 
termination.