# Enhanced Steganography for High Dynamic Range Images with Improved Security and Capacity
## 1 Introduction
These algorithms leverage the RGBE HDR encoding format to conceal a small quantity of messages; however, the capacity provided by these algorithms is limited to less than 0.5 bits per pixel. They are also known as distortion-free algorithms since any distortion produced after secret message embedding is negligible, resulting in a stego-image that is identical to the cover tone-mapped image after the tone-mapping operation. Due to the limited capacity offered by these distortion-free algorithms, it becomes challenging for them to support applications that require a large capacity. [PERSON] et al. [11] were among the pioneers to propose an HDR steganographic algorithm that conceals secret messages inside images in the Radiance RGBE format without impairing the image quality, making it undetectable to potential attackers. [PERSON] and [PERSON] [18] proposed a different approach for steganography in HDR images in RGBE format, leveraging the characteristics of the format to separate flat and boundary areas in cover images and embed data using two-side methods [19] with different strategies. [PERSON] et al. [12] introduced a data hiding scheme for HDR images in LogLuv format, which involves embedding data in the least significant bit (LSB) of the HDR image. The core of [PERSON] et al. 's method is inspired by the optimal pixel adjustment process (OPAP) [20; 21], which adjusts pixel values to minimize pixel variation after LSB replacement. However, most of the aforementioned research modifies steganography techniques originally designed for LDR images to apply to HDR images, rather than developing tailored approaches for HDR image formats. In a recent study, [PERSON] et al. [13] presented a data-hiding approach for HDR images in the RGBE format, which can be used for image annotation or steganography. The scheme proposed by [PERSON] et al. leverages the homogeneity present in the RGBE format to embed secret data. Building upon this work, [PERSON] et al. [14] (2016) proposed a novel data-hiding scheme for image annotation application by utilizing homogeneous representation groups more efficiently. However, it is noteworthy that potential vulnerabilities may exist in [PERSON] et al. 's data-hiding scheme when applied for steganography purposes. Motivation  
This research is centered around the steganography scheme proposed by [PERSON] et al. [13], which has an average capacity within the range of 0.0010-0.0026 bits per pixel. In order to fully leverage the strengths of [PERSON] et al. 's scheme tailored for HDR images, it is worth exploring potential methods of enhancing its capacity and security for steganography purposes. Our findings reveal that, while [PERSON] et al. 's scheme maintains imperceptibility in pixel differences before and after embedding, it suffers from a scarcity of embeddable pixels in general HDR images, potentially resulting in low capacity. Additionally, the embedding process disrupts the normal distribution of pixel values, which introduces potential weaknesses when stego-images are subjected to statistical analysis attacks. Thus, a potential security concern exists.