Short Message Service (sms) security solution for mobile devices

4. 
Analysis of Results 
Table 4 shows a summary of the performance measurement results. The 
input size for the clear text was arbitrarily chosen as 100kb for comparison. The 
respective key lengths chosen for the encryption represent typical key lengths in 
use today that are generally regarded as secure. 

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 49
 Key 
Length 
Block 
Size 
Input 
Size 
Time
(ms) 
Power 
Consumption 
(mAH) 
 (bits) 
(bytes) 
(kb) 
Mean 
Std Dev 
Mean 
Std Dev 
RSA 
1024 117 
100 
16212.31
164.44
107.00 
15.77
RSA 
2048 117 
100 
25643.18
40.16
157.68 
34.96
RSA 
2048 245 
100 
11458.50
1172.65
80.02 
24.34
AES 
128 16 
100 
536.53
3.74
2.41 
0.57
AES 
256 16 
100 
586.59
3.45
2.91 
0.39
Table 4. Performance Measurement Results 
The baseline measurement results are shown in Table 5. 
 Time 
 
(ms) 
Power Consumption 
(mAH) 
 
Mean 
Std Dev 
Mean 
Std Dev 
Baseline 
128.61
26.65
0.56 0.21
Table 5. Baseline Measurement Results 
Table 6 shows the adjusted performance results, after excluding all other 
operations not related to the encryption operation, such as data logging. 
 Key 
Length 
Block 
Size 
Input 
Size 
Time
(ms) 
Power 
Consumption 
(mAH) 
 (bits) 
(bytes) 
(kb) 
Mean 
Std Dev 
Mean 
Std Dev 
RSA 
1024 117 
100 
16083.70
191.09
106.44 
15.98
RSA 
2048 117 
100 
25514.57
66.81
157.12 
35.17
RSA 
2048 245 
100 
11329.89
1199.29
79.46 
24.55
AES 
128 16 
100 
407.92
30.39
1.85 
0.79
AES 
256 16 
100 
457.98
30.10
2.35 
0.60
Table 6. Adjusted Performance Measurement Results 
a. 
Performance Differences at Different Key Lengths 
For a fixed input block size of 117 bytes for RSA encryption, the 
timing performance for RSA encryption using a 2048-bit key length was about 58 
percent more compared to a 1024-bit key length, and consumed about 33 
percent more power. 
However, a larger block size of 245 bytes can be supported with a 
2048-bit key length, resulting in less number of encryption cycles required. With a 

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 50
245-byte block size, the timing performance was actually approximately 23% 
better than the performance at 1024-bit key length. The impacts of the key length 
and input size will be discussed further in a later Section. 
For AES encryption, the timing performance at 128-bit key length 
was approximately 12 percent faster than at 256-bit key length and consumed 
about 22 percent less power. The block size for AES encryption is fixed at 128 
bits (16 bytes). Therefore the total number of encryption operations to encrypt 
100kb of data is the same. However, the internal mixing cycles of AES algorithm 
increases with longer key lengths.