STUDY ON REVERSIBLE DATA HIDING TECHNIQUES FOR IMAGES

Abstract

With the advent of digitalization, a large amount of media data is being digitalized, and dig- ital storage stores data in a discrete form, which constitutes a part of media that is repre- sented by some discrete value, thus making them vulnerable to various attacks. Protection of data integrity is a major problem in the field of information security. Thus, cryptography and Information hiding mitigate these issues. In a cryptography-based system, the main idea is to change the data into an incomprehensible manner, but at least it reveals the mes- sage’s presence. Steganography helps to overcome the shortcomings of cryptography by hiding information in any digital media so that it is impossible for an individual to notice, but the digital media becomes useless when the secret gets revealed due to the damage caused by the data. However, most of the data hiding techniques suffer from permanent distortion of cover which makes their usage questionable in certain fields like defence, mil- itary image, medical diagnosis, digital forensics, stereo image coding etc, which cannot tolerate any distortion, as the retrieval of the cover media is as important as the hidden data. This is when the reversible data hiding method comes into picture. Reversible data hiding (RDH) is an innovative technique for data hiding that allows for the embedding of secret information into digital media such as images, videos, or audio files, with the crucial requirement that the original media can be perfectly restored after the hid- den data is extracted. The key distinction of RDH lies in its ability to achieve lossless embedding, where the host medium can serve dual purposes, i.e., securely carry the hid- den data and retain its original form upon data extraction. In the plain domain, the data hiding process is carried out directly on the original, unen- crypted host medium. In the encrypted domain, the host medium is encrypted before data hiding, ensuring that the original content remains confidential even during the embedding process. However, most of the techniques suffer due to the concerns about low data capacity, data security, and mainly in handling the communication overhead. To overcome these issues, a multistage high capacity reversible data hiding technique without overhead has been de- vi veloped where histogram peaks are exploited for embedding the secret data along with overhead bits both in the plain domain and encrypted domain, thus enhancing the embed- ding capacity, data security, lower bandwidth, and lesser time complexity. To further enhance the embedding capacity, communication overhead, and data security, a more complex yet efficient technique has been developed where both left peak and right peak from the main histogram peak have been exploited for data embedding. Most of the RDH techniques being interdependent, and the image recovery is possible only after the secret extraction processes. In an encrypted domain, access flexibility being a factor, the stakeholders allied will have different levels of access to the data. To en- sure privacy and security to both data and cover image, a separable reversible data hiding method in an encrypted image employing bit pair difference at the pixel level has been de- veloped. With an encrypted image containing data, the receiver can either extract secret information, decrypt the cover media, or do both, depending on the available keys. Thus, the spatial correlation in natural images won’t get exploited, ensuring high data embedding capacity. In the developed method, encrypted data is embedded in the cover image, there- fore enhancing the security of the secret data along with the cover image. It is very critical when it comes to secure communication of sensitive data over the public network, especially in the private or public 5G/6Gcellular network with tremendous de- ployment of the Internet of Things. Nowadays, most of the traffic over the communication channel is encrypted, and applications ensure end-to-end encryption of user data. Accord- ingly, solutions for data hiding over encrypted channels are invented that exploit redundant information or correlation among blocks of encrypted data for single user secure hiding of data. Thus, most of these communication networks and resources are underutilized as they offer high capacity transmission at multi-gigabit-per-second data rates. Therefore, a method has been developed where the user’s secret data is hidden over encrypted traffic at the byte level without any communication overhead. The method is independent of the type of cover and does not exploit the correlation among the traffic bytes. Here, embedding is possible, multiple times in a single traffic byte, thus enhancing the privacy and security of the data. The developed method allows multiple users to communicate over a common channel without affecting individual users; thus, effective utilization of the channel band- width and the resources can be attained. PSNR, MSE, POSP, NCC, and SSIM metrics are used to assess the imperceptibility of the image. The experimental validations over different types of cover have confirmed that the proposed techniques outperform the existing state-of-the-art techniques.