**6.4 Encryption algorithm speed**

In real-time application, the run time is considered as a main constraint. Eqs. (11) and (12) are used to calculate the speed (*S*) and the number of cycles per byte obtained by a specific algorithm running on the processor.

#### *Lightweight Cryptographic Techniques and Cybersecurity Approaches*


#### **Table 8.**

*Entropy and correlation values.*


**Table 9.**

*Performance results and comparison with the state of the art.*

$$\text{SS} = \frac{\text{data size}}{\text{Time}} \text{MB/s} \tag{11}$$

$$number\text{ of cycles}/\text{byte} = \frac{Frequency}{\text{S}}\tag{12}$$

A comparison with related works is given in this state (**Table 9**). The comparison proves that the suggested scheme has the best findings in terms of speed.

## **7. Conclusion and future work**

In this paper, we have put forward a strong hybrid cryptographic framework for image encryption, decryption, and authentication. The algorithm has combined a hash function and symmetric and asymmetric algorithms. The keccak hash function has been used for the initial secret key generation related to the plain image and owner's signature. The RSA encryption system has been used for the secret key exchanging and authentication. For image encryption, we have utilized the AES-256 bits with CTR mode. The main advantages of this mode are the rapidity of treatment and the no error propagation. The evaluation and analysis results prove that our proposed algorithm allows high performance and security. It can resist most known cryptanalysis attacks. For future work, we aim to design a mechanism for dynamically changing the S-box values of the AES.

*Hardware Implementation of an Improved Hybrid Cryptosystem for Numerical Image Encryption… DOI: http://dx.doi.org/10.5772/intechopen.105207*
