# A Novel Adaptive Image Data Hiding and Encryption Scheme Using Constructive Image Abstraction
## 1 Introduction
[23] used the AES encryption algorithm on 16-pixel image blocks and embedded 1-bit data into a randomly chosen pixel using a pseudo-random number generator. In contrast, for the RRBE approach, [PERSON] et al. [24] reserved room by histogram shifting, significantly increasing the payloads. After two pioneering studies, several improvement schemes have been proposed [25]. For example, [PERSON] and [PERSON] [26; 27] utilized error prediction and the LOCO-I algorithm in the JPEG-LS compression standard to achieve an average embedding rate of 2.46 bpp. Meanwhile, [PERSON] et al. [28; 29; 30] employed a block-level approach for reversible data hiding in the encrypted domain, achieving a maximum embedding rate of 2.5 bpp. These VRAE or RRBE algorithms focus on providing large payloads but fail to evaluate the security of encrypted images. This paper presents a new adaptive data hiding method which conceals messages when constructing an HDR abstracted image. To the best of our knowledge, few works in the extant literature report on data hiding on abstracted HDR images. Our scheme is suitable to embed secret messages when rendering HDR RGBE and LDR abstracted images. Furthermore, our algorithm performs adaptive data hiding based on the brightness of pixels, where more data are concealed in darker pixels without upsetting the human visual system. Moreover, in order to further protect the image content and the concealed message, we recommend an image encryption algorithm that utilizes a two-dimensional logistic tent modular map (2D-LTMM) [31] and a random permutation scheme [32]. This encryption algorithm is also suitable both for HDR RGBE as well as LDR images. To ensure the security of our image encryption scheme, we evaluated its security using the metrics suggested by [PERSON] et al. [14] and conducted a noise addition analysis. Our work has the following contributions:  
* Our algorithm conceals messages during the image abstraction process which belongs to the constructive image steganography (CIS) approach rather than the SCM approach; it is suitable for both HDR RGBE and LDR images. Our scheme effectively eliminates the vulnerability associated with the SCM approach because the CIS approach offers a significant benefit of producing no cover image. It is difficult for a steganalytic tool to take any advantage to fully train models to distinguish the difference between cover and stego images. Consequently, our scheme can resist training-based steganalysis attack. * Our adaptive approach conceals a greater number of confidential data in darker and lower luminance pixels, while embedding fewer messages into brighter and higher luminance pixels. This adaptive technique is consistent with the human visual system: dark pixels are less sensitive to the human eye, and minor changes in brighter regions are more apparent. Our algorithm delivers higher embedding rates, ranging from 14% to 33% compared to the current state-of-the-art techniques, while maintaining the quality of a stego image. * We propose an encryption algorithm that is suitable for both RGBE-based HDR images and LDR images. By utilizing a 2D-LTMM, this scheme produces pseudo-random sequences with improved hyperchaotic characteristics. In addition, exploring a simple yet efficient random permutation scheme enables our scheme to perform not only the bit-level permutation, but also the byte-level diffusion. As a result, our scheme encrypts all bits in all channels in RGBE and LDR images. * Our encryption algorithm was thoroughly assessed through seven metrics. The outcomes demonstrate that our encryption scheme offers robust security against statistical, differential, brute force, chosen-plaintext, and chosen-key attacks. The remaining sections of this paper are structured as follows: In Section 2, we elaborate on our proposed methods, which consist of image abstraction, adaptive data embedding, data extraction, image encryption, and image decryption. In Section 3, we outline the experiment results and compare them against other relevant schemes.