For secure communication between sender and receiver in this digital world over internet, cover steganography plays a vital role and flourishing research area. For digital steganography, many research works have been proposed over the last decades such as LSB, pixel value differencing, randomization, cyclic, etc. and each has their related pros and cons. Notably, for inserting the mystery message inside the cover media the most well-known and habitually utilized strategy is the LSB technique [17]. The wide uses of this technique is due to its simplicity and straightforwardness. Therefore, this section elaborates the basic concepts of RGB and HSI color model, Least Significant Bit (LSB) and critically analysis of some methods presented in literature [18].
However, how about we make sense of RGB and HSI variety models; one of the main parts of any item is its tone.
The utilization of variety in picture handling is persuaded by standard two aspects.
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From a scene, that often streamlines object identification and abstraction, a color is a powerful descriptor.
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Contrasted with about just too many shades of gray the people can discern thousands of color shades and intensities.
The second is predominantly significant in physical image analysis (i.e. when performed by people). The purpose of color model or color system is to facilitate the specification of colors in some standard, and generally accepted way, when working in image processing because it the main part of it. Each color tone is addressed by a solitary point, because color mode is a description of a coordinate system and subspace within that system. In practice most commonly used color models; Red, Green, Blue (RGB) model used for monitors and a broad class of color video cameras because it is the hardware-oriented models in terms of digital image processing. For printing the second color model used is Cyan, Magenta, Yellow and Black (CMYK), Cyan, Magenta, Yellow (CMY). To corresponds closely with the way humans, describe and interpret color, the third color model Hue, Saturation, Intensity (HSI) is used. So, the main focus of this study is HSI model. In HSI color Model, changing from one model to the other is an open process while creating colors in the RGB and CMY models [19]. For hardware implementations, ideally suited is this color system. The RGB framework coordinates pleasantly with the way that the natural eye is firmly viewpoint to red, green, and blue primaries. Yet, the RGB, CMY, and other comparable variety models are not appropriate for depicting colors in wording that are pragmatic for human translation.
For instance, one doesn't allude to the shade of color by giving the level of every one of the primaries creating its tone. Besides, we don't consider a variety of pictures as being made out of three essential pictures that join to frame that solitary picture [20]. So, we describe by its hue, saturation, and brightness, when human view a color object. Hue is a color aspect that defines a clean color (i.e. Yellow, red, and orange), while saturation gives a measure of the degree to which a pure color is diluted by a white light. Whereas intensity is a particular descriptor that is basically difficult to gauge. It is one of the key aspects in describing the color sensation, and it also exemplifies the colorless thought of intensity. This quantity absolutely is measurable and simply interpretable because it is an utmost convenient descriptor of monochromatic images. In a color image, the HSI model decouples the intensity component from the color carrying information (hue and saturation). Based on color descriptions HSI color model is an ideal tool for developing image processing algorithms because that are naturally intuitive to humans. For color generation, we can say that RGB is ideal tool, but for color description it is significantly more restricted. Hereafter, from in RGB image we should be capable to excerpt intensity [21–22]. However, HSI color model plays a vital role in secret information camouflage because Intensity plane (I Plane) does not grief the other planes, unique RGB diverts in which all planes are unequivocally co-related with one another. Besides, handling an image in HSI model is somewhat more economical based on LSB based technique etc. So, LSB is the process of embedding the secret message into cover image pixels of LSB’s either randomly or sequentially shown in Fig. 2 [23–25]. The given figure explores the concept of LSB by taking the cover image converting into their corresponding American Standard Code Information Interchange (ASCII) values then converting into binary values [26].
After reading the image pixels’ values and its binary forms it converts the secret message values to binary form [27]. Furthermore, it the procedures of implanting secret data bit K replace with cover image pixels K LSB’s. Eq. 1 represents the embedding process.
SIM (i, j) = CI (i, j) − CI (i, j) mod 2K +SM (i, j) Eq.1
Where SIM (i, j) presents the stego image i, j represents row and column, CI is cover image and SM secret message. Different LSB based methods are proposed recently but that still have issues to improve this research area. Human eye is very naked and having properties to detect or suspect little change in any smooth area of the images [28]. So, encrypting the secret message with the image either randomly or sequentially and not all pixel values is used for embedding so the change may be happening on only the embedding area of the image. Therefore, various image steganographic reported works are adapted to embeds suitable amount of message in appropriate cover object [29].
Lee et al. recommended a high implanting message based image steganography where they embedded 12 KB cover information inside the cover image and the technique focused only on payload [30]. Zang and Wang et al. introduced proficient steganographic inserting by taking advantage of the alteration course. The author focused on embedding more message also try to get security [31].
Khan et al. offered a cyclic image based steganography method using randomization. In this paper authors struggled to get the consistency among the basic criteria and embedded 4 to 8 KB secret message. Karim suggested new image steganography technique in light of LSB using secret key and achieving the security, payload but broke down the other criteria [32].
Muhammad and Sajjad proposed and magic LSB method using multi-level encryption and HSI image. It is a better technique in image steganography but having some limitation to different attacks such as scaling, noising, cropping etc. [33
Rustad et al developed a novel image steganography for improving the perceptual transparency of the image. It is an inverted LSB method using adaptive pattern. This research achieved a high quality stego image but the payload limit is too low [34].
Cheng, X., & Huang proposed a novel method of reversible encrypted image based steganography using interpolation image and histogram shifting. In this study the author used double scrambles operation on pixel of the image by changing the positions of the pixels. The experimental results achieved a high embedding capacity and security [35].
Shwe Sin et al. presents a LSB and Huffman code based steganography. The investigational outcomes presented that the algorithm got high embedding capacity and better security [36].
Tsai et al presented another lsb based image steganography algorithm in light of MSB prediction and Huffman base method. The main objectives of the paper are high payload and secrecy and increase the inserting pace of the mystery message inside the cover picture [37].
M. Shahu et al. present a novel technique, LBP-based reversible information stowing away effectively accomplishes better HC, SI quality, and strength to different assaults. Be that as it may, besides these benefits, the proposed method can be improved concerning HC. Since the proposed work utilizes the LBP-based strategy, subsequently, it considers the surface and smooth pictures as unclear while embedding the EBs. Regardless, the pixel power of surface pictures makes it more sensible to introduce more EBs when appeared differently in relation to smooth pictures. Thusly, the proposed work can be contacted to achieve higher HC in surface pictures by brushing LBP with the PVDS-based technique [38].
A.K. Sahu et al proposed a better method for two delicate watermarking plans to perform altering recognition and limitation in a picture. The proposed plans were outwardly disabled and the watermark pieces were created using the turbulent system based determined map at both the source and getting end. Further, the chief contrives saw a constraint of ± 1 contrast between the host and watermarked pixels. As such, the idea of the watermarked picture was far superior to that of various plans. Finally, surprising results were achieved in regards to the adjusted area and limitation limit of the proposed plans. Later on, the proposed work can be connected with self-recovery of the modified pieces, and growing both spatial and change spaces to extra overhaul the force [39]. There are different reported works presented in the literature based on image steganography, and each method has its related advantages and disadvantages depending on its embedding procedures and selection of the cover object [40]. Moreover, every examination work has attempted to cover the rudiments standards of picture steganography such are payload, strength, discernment, temper insurance, and computation. Some examination of existing techniques is introduced in Table 1.
Table 1
Critical analysis of various existing method using criterion of image steganography
Techniques | Pros | Cons | Measuring Algorithm |
Capacity | Security | Transparency | Temper Protection | Computation |
Canny edge detector [41] | High Security and resistance | Low quality and payload | No | Yes | No | Yes | Yes |
Huffman Encoding [42] | high capacity and a good invisibility | secure less | Yes | No | Yes | Yes | No |
Huffman coding and the LSB replacement [43] | embedding capacity, security and imperceptible | Can’t resist against attacks and time consuming | Yes | Yes | Yes | No | No |
adaptive Huffman code mapping (AHCM) [44] | Higher secure payload | Low quality image | Yes | Yes | No | No | Yes |
AES–Huffman Coding–DWT [45] | good stego image quality and security | Can’t resist against attacks and time consuming | Yes | Yes | Yes | No | No |
Enhanced Huffman-PSO based image optimization algorithm [46] | Payload, and quality images | Secure less and time consuming | Yes | No | Yes | No | No |
P single/P double and Huffman Coding [47] | imperceptible, and robust | Time consuming and can’t resist | Yes | Yes | Yes | No | No |
IS method based on pixels variance, eight neighbors [48] | Capacity, and securable | Low quality images | Yes | Yes | No | Yes | No |
deflate compression for image steganography [49] | imperceptible, and robust | Time consuming and can’t resist | Yes | Yes | Yes | No | No |
image steganography using pixel allocation and random function techniques [50] | security and imperceptibility | Low payload and time consuming | No | Yes | Yes | Yes | No |
Unlimited Secret Text Size IS [51] | Payload, and quality images | Secure less and time consuming | Yes | No | Yes | No | No |
HC, minimum distortion based on distinction grade value [52] | high embedding capacity, security and visual quality | Can’t resist against attacks and time consuming | Yes | Yes | Yes | No | No |
Reversible data hiding with adaptive Huffman code [53] | greater embedding rate and improved security. | Low quality and consuming | Yes | Yes | No | Yes | No |
fragile watermarking based on Huffman [54] | increasing safety and security | Low payload limit and low quality, consuming | No | Yes | No | Yes | No |
Reversible, Time-Varying Huffman Coding Table [55] | Security, temper protection | Low payload limit and low quality | No | Yes | No | Yes | Yes |
Using RSA Algorithm [56] | Security, temper protection, quality | Payload, and time consuming | No | Yes | Yes | Yes | No |
In sum-up, Table 1expounded the analysis of the diverse existing methods using the basic criterion of steganography. And also expounded on the techniques used, the pros and cons, the main focus, the embedding procedure, and the limitations of each method. Though, after a detailed analysis of the existing methods many points come to mind, but some point is very vital; one is selecting an appropriate cover object and the second is the reliability between the essential criterion of steganography. Because some tried for making a reliable method but get one or two parameters but broke down the other criteria and also the reliability between the criterion which is an essential part of steganography. However, to tackle these vital needs, the proposed algorithm is designed in a manner that shows that which dimension of the image is better for which size of secret message and also to make a reliable method. However, the detail whole process of proposed algorithm is presented in next section.