Results of Verification Phase

Figure 6.24: The Impact of Probability of Detection on Processing Time during Response Phase for Large Scale Files When Signature Length is 256.

Figure 6.25: The Impact of Normal File Size on Processing Time during Verification Phase When the Signature Length is 16.

the verification of the outsourced blocks is only checked on the basis of the response and challenge messages without requiring the content of the original blocks.

The effect of probability of detection on the processing time of the verification phase is analyzed in Figure 6.26 for 16 bit signature. When the size of input file is 10 MB, the processing time of verification phase for 90%, 95%, and 99% probability is about 229.60 ms, 232.60 ms, and 244.60 ms respectively. The graph also shows that by augmenting the file size to 50 MB, the processing time raised slightly to 230.40 ms, 233.20 ms, and 244.60 ms.

The computation time of verification phase for 32 bit signature is displayed in Figure 6.27 to demonstrate the effect of file size. The result shows that the file size has not been the considerable impact on the variation phase. For example, the computation time for 90%, 95%, and 99% probability is about 64 ms, 69 ms, and 70 ms orderly.

The effect of probability of detection on verification phase with 32 bit signature is

Figure 6.26: The Impact of Probability of Detection on Processing Time during Verifica-tion Phase for Normal File Size When Signature Length is 16.

Figure 6.27: The Impact of Normal File Size on Processing Time during Verification Phase When the Signature Length is 32.

Figure 6.28: The Impact of Probability of Detection on Processing Time during Verifica-tion Phase for Normal File Size When Signature Length is 32.

shown in Figure 6.28. When the size of file is 10 MB, the imposed processing time on the auditor for 90%, 95%, and 99% probability is 64 ms, 68.40 ms, and 70.20 ms orderly.

Such cost for 50 MB file is around 63.80 ms, 68.80 ms, and 70.80 on the basis of the rate of detection.

Figure 6.29 explains the impact of file size on processing time of verification phase with 64 bit signature. This graph also proves that the rate of such cost is approximately constraint and is independent from the size of file (31 ms for 90% probability, 32 ms for 95% probability, and 35 ms for 99% probability of detection).

Figure 6.30 shows the effect of probability of detection on processing time of veri-fication phase with 64 bit signature. Clearly the processing time of veriveri-fication is around 30.80 ms, 32 ms, and 34.80 ms for 90% 95%, and 99% probability of 10 MB file. When the size of file raise to 50 MB, the computation time approached 30.80 ms, 32.20, and 35.20 ms for different rate of detection.

Figure 6.29: The Impact of Normal File Size on Processing Time during Verification Phase When the Signature Length is 64.

Figure 6.30: The Impact of Probability of Detection on Processing Time during Verifica-tion Phase for Normal File Size When Signature Length is 64.

Figure 6.31: The Impact of Normal File Size on Processing Time during Verification Phase When the Signature Length is 128.

The effect of file size and probability of detection on processing time of verification phase with 128 bit signature are illustrated in Figure 6.31 and Figure 6.32 respectively.

Figure 6.31 demonstrate that such cost has an insignificant fluctuation (from 18.40 ms to 18.80 ms for 90% probability, 19.60 ms to 19.80 ms for 95% probability, and 20 ms to 20.20 ms for 99% probability).

In Figure 6.32, it is clear that the probability of detection has a direct relation with processing time of verification phase. For example, when the size of file is 10 MB, the computation time is around 18.40 ms, 19.60 ms, and 20.20 ms on the basis of probability of detection.

We conducted such experience to analyze the effect of file size and probability of detection on processing time of verification phase for 256 bit signature in Figure 6.33 and Figure 6.34. From Figure 6.33, it can be understood that the computation time is independent from the file size, and it is about 11.80 ms, 12.60 ms, and 13.40 ms for 90%,

Figure 6.32: The Impact of Probability of Detection on Processing Time during Verifica-tion Phase for Normal File Size When Signature Length is 128.

Figure 6.33: The Impact of Normal File Size on Processing Time during Verification Phase When the Signature Length is 256.

95%, and 99% probability orderly.

Figure 6.34: The Impact of Probability of Detection on Processing Time during Verifica-tion Phase for Normal File Size When Signature Length is 256.

Figure 6.34 proves that the processing time of the verification phase only depends on the probability of detection. For instance, when the size of file is 30 MB, the processing time is increasing from 11.80 ms to 13.60 ms by increasing the rate of detection from 90% to 99%.

The comparison of the processing time for different probability of detection during the verification phase is shown in Figure 6.35. It can be seen that there are the direct relationships between the processing time and the probability of detection. As a result, by increasing the probability of detection from 90% to 99%, the rate of processing time is also increasing. This is because the auditor must use more blocks of the file (on the basis of the number of blocks in the challenge message) to verify the integrity of the outsourced file. On the other hand, the length of signature and the processing time has the inverse relationship due to decreasing the number of sectors for computing the signature.

Therefore, the minimum processing time of the verification phase is in 256 bit signature,

Figure 6.35: The Comparison of the Probability of Detection and Signature Length with Processing Time during the Verification Phase.

and the maximum cost is in 16 bits. Finally, the graph demonstrates that the processing time is independent of the size of file.

To ensure that the size of file has not a significant effect on the processing time, an experiment is conducted to check the integrity of large-scale file size (between 1GB – 10 GB). Figure 6.36 analyzes the impact of large-scale files on the processing time of verification phase with 256 bit signature. It is easily perceived when the probability of detection is 90%, 95%, and 99%, the processing time is in the range of 12.20 ms to 12.80 ms, 13 ms to 13.40 ms, and 15.80 ms to 16 ms respectively.

The effect of probability of detection on the processing time is also evaluated in Figure 6.37 (When the confidence interval is 99%). The graph shows there is a direct relation between the processing time and such probability in large-scale file size (as same as the normal file). For instance, the processing time of 5 GB file fluctuates between

Figure 6.36: The Impact of Large Scale Files on Processing Time during Verification Phase When Signature Length is 256.

Figure 6.37: The Impact of Probability of Detection on Processing Time during Verifica-tion Phase for Large Scale Files When Signature Length is 256.

12.40 ms and 15.80 ms on the basis of the rate of detection.