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Efficient Method to Message-Image Cryptography Using Reordered Image-Key

Rashad J. Rasras^* | Mutaz Rasmi Abu Sara | Ziad Alqadi

Department of Electrical Engineering, Al-Balqa' Applied University, Amman 11134, P.O. Box 15008, Jordan

Faculty of Engineering and Information Technology, IT Department, Palestine Ahliya University, Bethlehem 1041, Palestine

Corresponding Author Email:

rashad.rasras@bau.edu.jo

Received:

19 September 2022

Revised:

16 January 2023

Accepted:

30 January 2023

Available online:

28 February 2023

| Citation

ts_40.01_22.pdf

OPEN ACCESS

Abstract:

Color image may be secret or holding secret data, also secret messages may be so confidential. To protect these data, we have to use a simple and efficient method. In this research a method of data encryption-decryption will be presented. The suggested method will use a complicated PK to apply image encryption/decryption using XORing operation, the used image key will be reordered using a secret ordering sequence. Any modifications made to the PK during the decryption process will be regarded as a hacking attempt and result in corrupted decrypted data; hence, the encryption and decryption processes must employ the same secret information. The PK will provide an enormous key space that could resist any type of hacking attempts. The suggested method will be tested and the obtained results will be compared with those of DES and AES, the throughputs and speedup will be calculated. It will be shown how easily we can use encrypt decrypt color images with any size using a fix image key, and it will be shown how the suggested method maintain desirable values of MSE and PSNR parameters.

Keywords:

cryptography, flipping, image_key, MSE, PSNR, resizing

1. Introduction

The process of encrypting and decrypting data [1, 2] is an important process in order to protect confidential text messages or protect digital images from tampering with intruders by not enabling them to understand confidential data [3, 4].

Most encryption operations depend on the use of a private secret key [5-7], as this key is used in the process of executing some specific operations on the secret data to generate destructive and incomprehensible data [8, 9] as shown in the Figure 1. In order to generate data that is similar to the original secret data without ever losing any data or any part of it, the decryption process is carried out using the specified operations on the secret key and the encrypted data [10-12].

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Figure 1. Encryption-decryption process

Confidential data is circulated, whether short messages, long messages or digital images that could be a personal nature or carry sensitive data through many different social media, which calls for preventing third parties from accessing and viewing this data [13-15].

The majority of the approaches used today to protect sensitive data are based on DES and AES standard methods. Although DES is fast to encrypt and decrypt data, it lacks security due to the short length of the used public key, which makes it susceptible to hacking by outside attackers. The U.S. government selected AES as its symmetric block cipher because it was designed to be easy to implement in hardware and software, as well as in limited environments, and to give strong protections against a variety of attack.

Jose et al. [16-18] introduced steganography methods of data hiding and extracting based on the least significant bit (LSB)] [17, 18]. The LSB technique was modified, and improved, to increase its level of protection [19]. LSB is an unsecure method of hiding secret messages, and the process of data hiding can be implemented by reserving 8 bytes of the holding image to store one character of the message. LSB requires the binary code of the character, and each bit of this code can be inserted in the least bit of the selected byte of the holding image. The benefits of using LSB-based approaches are low MSE and high PSNR [20], which make changes in the holding image difficult for the human eye to notice.

Sivakumar and Venkatesan [21] suggested matrix reordering based method of color image encryption -decryption with an average throughput. The security level and efficiency parameters of this method were increased, but a large amount of memory space was needed for the private secret key due to its size and complexity. Gao et al. [22] suggested method of image encryption on the base of a chaotic algorithm using the power and tangent functions rather than linear functions. In this method One-time-one-password encryption is used, which is more secure than the DES algorithm (although not secure enough). Additionally, it includes inefficient parameters that lead to slow encryption-decryption process and low performance. Asymmetric color image encryption-decryption was realized using a matrix transformation; however, the throughput was low due to the long encryption-decryption processes [23]. A method of image encryption method based on matrix decompositions is suggested, where the order and rank of the deconstructed components serve as unique key parameters [24]. Wang and Zhang [25] suggested a chaos-controlled poker shuffle operation based method of color image encryption-decryption. The drawback of both versions of this method was its poor throughput.

Accordingly, any method can be adopted, provided that the following requirements are met:

In order to give a high level of data confidentiality and protection the suggested technique must employ secret key that is hard for hackers to penetrate [26].
The quality factors values must be acceptable. MSE and PSNR are factors that are used to evaluate the quality of suggested method (see Eqns. (1) and (2)). If the data was destructed then the calculated value of MSE for the original and encrypted data must be very high, whereas PSNR should be very low (see Table 1). Calculated value of MSE for original and decrypted data should equal zero, whereas PSNR must be infinite [27, 28].
The suggested method must be effective by reducing encryption decryption times and increasing method throughput. (bytes manipulated in second) [29-31].
The suggested method should be easy to implement.

MSE between S and R, n: message length

$M S E_{S R}=\frac{1}{N} \sum_{j=0}^{n-1}[S(j)-R(j)]^2, N=n$ (1)

$P S N R_{S R}=10 \times \log _{10} \frac{\left(M A X_j\right)^2}{M S E_{S R}}$ (2)

Table 1. Quality factors

	Original		Encrypted		Decrypted
	MSE	PSNR	MSE	PSNR	MSE	PSNR
Original	-	-	High	Low	Zero	Infinite
Encrypted	High	Low	-	-	High	Low
Decrypted	Zero	Infinite	High	Low	-	-

Digital color image is huge incubator of data, it represents a set of three bytes, where each of byte carries the information about the red, green and blue colors (RGB), producing a total of 24 bits per pixel in the source imager. So the image may be represented by 3 dimensions for red, green, and blue as illustrated in Figure 2.

The color image may be easily employed as PK, this key is simple to manipulate. The key preprocessing in this research will focus on image flipping and image resizing, these operations are explained in the Figures 3, 4, and 5.

In our proposed method we will use the reordering sequence, this sequence contains 3 parameters with values 1 or 2, 1 means that the color matrix flipped row-wise down, 2 means the color matrix is flipped column wise left to right (for example the sequence 1 2 2 means: red color is flipped row-wise, green color is flipped column wise, blue color is flipped column wise, Figure 6 shows how a color image is reordered using the sequence.

image006.png

Figure 2. Color image representation

image007.png

Figure 3. Image flipping

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Figure 4. Image resizing to meet the message length

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Figure 5. Image resizing to meet another message size

image010.png

Figure 6. Using reordering sequence

2. The New Suggested Method

The new suggested method provides a special PK which includes the image-key (which must be kept confidential and without transmission) and the reordering sequence, By using this PK we can apply encryption process as shown in Figure 7, and decryption process as shown in Figure 8:

image011.png

Figure 7. Proposed encryption phase

image012.png

Figure 8. Proposed decryption phase (example)

The encryption process could be implemented by performing the following steps (an example is shown in Figure 7):

Step 1: Select the image_key.