**3.6 Performance evaluation**

Performance measurement criterion is the time taken by the algorithms to perform encryption and decryption of the input text file, that is, the encryption computation time and decryption computation time. [20]

#### *3.6.1 Computation time for encryption and decryption*

The encryption computation time of the encryption algorithm is the time taken by the algorithm to produce the ciphertext from the plaintext. The encryption time can be used to calculate the encryption throughput of the algorithms.

The decryption computation time is the time taken by the algorithms to produce the plaintext from the ciphertext. The decryption time can be used to calculate the decryption throughput of the algorithms.

For evaluation, files of sizes 1, 2, 5, 10, 20, 40, 60, 100 and 200 KB were used as input data files. For the sake of comparison, same input files have been set as input to both HGEA and DES. [14] DES has also been implemented in the same environment, JAVA version 8 and simulated in IntelliJ IDEA v.2018.1.4 on the same machine (**Tables 10** and **11**).

The same data set was encrypted via both DES and HGEA algorithms. Each sample data set was encrypted with five randomly chosen passwords, and the encryption execution time and decryption execution time were listed as shown in **Table 12**.

The whole test was performed very carefully. During the test, it was observed that sometimes, when new input data are fed into the computation model, the test results returned false encryption and decryption time values; for example, the test model resulted in very high encryption and decryption execution time values or the test model's decryption execution time was very high compared to encryption computation time and the decrypted plaintext differed from input plaintext. So to resolve this issue, a new terminal was generated in Intellij whenever the input value was changed.

The average values of execution time for encryption and decryption were computed and are tabulated in **Tables 12** and **13**.


**Table 10.** *Execution time of DES.*


The above tabulated values represent the computation time of various sizes of sample data sets being processed by DES and HGEA. Results show that for the proposed HGEA, execution time is 26, 49 and 62 for 1, 5 and 10 KB of data, respectively. HGEA has a much slower execution time compared to DES. The execution time of the proposed algorithm increases with an increase in data size. Further, by using the values of **Tables 12** and **13**, various graphs showing the encryption execution and decryption execution times for DES and HGEA with

The above graph shows that the throughput of DES is considerably better than HGEA for small-size input files and it increases with an increase in file size compared to HGEA. It also shows that encryption time for both algorithms is more than

The variation in encryption time and decryption time in HGEA is due to steps followed during decryption. During encryption process in the transformation step,

different input sizes were generated as shown in **Figure 5(a)–(c)**.

decryption time.

**157**

**Table 12.**

**Table 13.**

*Computation time of encryption for various input sizes.*

*Hybrid Approaches to Block Cipher*

*DOI: http://dx.doi.org/10.5772/intechopen.82272*

*Computation time of decryption for various input size.*


#### **Table 12.**

For evaluation, files of sizes 1, 2, 5, 10, 20, 40, 60, 100 and 200 KB were used as input data files. For the sake of comparison, same input files have been set as input to both HGEA and DES. [14] DES has also been implemented in the same environment, JAVA version 8 and simulated in IntelliJ IDEA v.2018.1.4 on the same

The same data set was encrypted via both DES and HGEA algorithms. Each sample data set was encrypted with five randomly chosen passwords, and the encryption execution time and decryption execution time were listed as shown in

The whole test was performed very carefully. During the test, it was observed that sometimes, when new input data are fed into the computation model, the test results returned false encryption and decryption time values; for example, the test model resulted in very high encryption and decryption execution time values or the test model's decryption execution time was very high compared to encryption computation time and the decrypted plaintext differed from input plaintext. So to resolve this issue, a new terminal was generated in Intellij whenever the input value

The average values of execution time for encryption and decryption were com-

machine (**Tables 10** and **11**).

*Computer and Network Security*

puted and are tabulated in **Tables 12** and **13**.

**Table 12**.

was changed.

**Table 10.**

**Table 11.**

**156**

*Execution time of HGES.*

*Execution time of DES.*

*Computation time of encryption for various input sizes.*


#### **Table 13.**

*Computation time of decryption for various input size.*

The above tabulated values represent the computation time of various sizes of sample data sets being processed by DES and HGEA. Results show that for the proposed HGEA, execution time is 26, 49 and 62 for 1, 5 and 10 KB of data, respectively. HGEA has a much slower execution time compared to DES. The execution time of the proposed algorithm increases with an increase in data size.

Further, by using the values of **Tables 12** and **13**, various graphs showing the encryption execution and decryption execution times for DES and HGEA with different input sizes were generated as shown in **Figure 5(a)–(c)**.

The above graph shows that the throughput of DES is considerably better than HGEA for small-size input files and it increases with an increase in file size compared to HGEA. It also shows that encryption time for both algorithms is more than decryption time.

The variation in encryption time and decryption time in HGEA is due to steps followed during decryption. During encryption process in the transformation step,

encryption algorithms. Also, the multiple transformation, multiple key generation provides, combined with graphical interpretation provided added security to the algorithm. The realization of computation model proved the proposed encryption algorithm is practically realizable. Further comparative analysis of computation

Although the comparative analysis of proposed model is proven to be more secure, the model was slower than DES. However, the processing units of modern day computer system are extremely high and developing rapidly, the implementa-

time of realized model was made.

*Hybrid Approaches to Block Cipher*

*DOI: http://dx.doi.org/10.5772/intechopen.82272*

tion of HGEA possible.

**Author details**

**159**

1 Nepal Open University, Nepal

Roshan Chitrakar1,2\*, Roshan Bhusal2 and Prajwol Maharjan<sup>2</sup>

2 Nepal College of Information Technology, Nepal

provided the original work is properly cited.

\*Address all correspondence to: roshanchi@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

**Figure 5.** *File size vs. execution time of DES and HGEA.*

each Mi is XOR-ed with all of the possible subkeys and only one of four possible 4 4 matrices is chosen for further processing. However, during decryption in the transformation step, only one 4 4 matrix is directly generated depending upon selected quadrant value. So, the generation of all of the possible intermediate values is one of the reasons for variation of encryption and decryption times in HGEA.

### **4. Conclusion**

The DNA cryptosystem containing DNA hybridization technique and secure key generation technique OTP are studied, explained and implemented by taking input from the DES algorithm output. The output of DES-based DNA cryptography algorithm has encrypted message in the form of DNA sequences and the decrypted message is the original plaintext.

The DDHO algorithm is tested on different types of plaintext; the encryption and decryption times are calculated; the analysis of length of plaintext, length of ciphertext and size of key is done and found that the length of ciphertext is proportional to the corresponding plaintext length. The encryption and decryption times increase slower with the changes in the length of plaintext.

From the process of analyzing various cryptographic algorithms, a unique encryption algorithm "hybrid graphical encryption algorithm" has been proposed. The algorithm was based on hybrid cubes encryption algorithm (HiSea). The features like graphical interpretation and computation of selected quadrant value are the unique features of this algorithm, which is different from existing standard

#### *Hybrid Approaches to Block Cipher DOI: http://dx.doi.org/10.5772/intechopen.82272*

encryption algorithms. Also, the multiple transformation, multiple key generation provides, combined with graphical interpretation provided added security to the algorithm. The realization of computation model proved the proposed encryption algorithm is practically realizable. Further comparative analysis of computation time of realized model was made.

Although the comparative analysis of proposed model is proven to be more secure, the model was slower than DES. However, the processing units of modern day computer system are extremely high and developing rapidly, the implementation of HGEA possible.
