# Evaluation of a Framework for Robust Image Reversible Watermarking
## 1 Introduction  
Due to available fast Internet connections, massive access to multimedia material is common currently. However, this ease of connection produces some risks in the reliability of the accessed material. Although different strategies have been proposed, in particular, digital watermarking has been shown to be an appropriate option for the protection of multimedia content. Despite its protection capabilities, conventional digital watermarking produces distortion in the host signal. These distortions are not acceptable for critical applications such as medical or military imaging [1]. Reversible watermarking schemes (RWSs) emerge as an option to overcome the distortion induced by classical marking schemes. RWSs allow the host signal to be reconstructed to its original state after removing the inserted watermark. On the other hand, most of the RWSs are not very robust to attacks. If a tagged signal is attacked, the recovery of the information and the reconstruction of the host signal will be very difficult. Recently, some robust reversible watermarking schemes have been proposed in the literature. Most of these schemes are deployed in the spatial domain and are robust to JPEG compression and the addition of Gaussian noise. Some examples of this kind of scheme are the ones presented by [2; 3]. Furthermore, there are schemes that use the frequency domain for the insertion of the watermark. As is well known, the frequency domain is usually more robust to attacks than the spatial domain. There are some examples of such schemes in the literature, such as those proposed in [4; 5; 6]. Typically, these schemes are robust to attacks such as clipping, noise addition, scaling, and histogrammodification. Furthermore, RWSs for medical images have been recently proposed under a hybrid approach such as in [7]. An interesting watermarking application is known as signal authentication, where a fragile watermark is used to identify and localize tampering in the attacked signals. A representative fragile watermarking scheme for medical images is reported in [8]. Due to the need to restore the attacked signals, beyond identifying the attack, self-recovery schemes have emerged. In [9], the idea was proposed of embedding an image into itself to restore the tampered regions; this is the first self-recovering scheme proposed in the literature. The steps typically followed by self-recovering schemes are: obtain a compressed version of the host signal and insert this version into the host signal itself. Upon detection, using a fragile watermark, of an attacked region, it is possible to restore it using the compressed version originally inserted into the host signal. It has been observed in the literature that there are two types of results delivered by self-recovery schemes: approximate recovery and perfect recovery. The former refers to the ability to recover the attacked signal to levels of high similarity with the original one, while perfect recovery refers to the fact that the recovered signal will be exactly the same as the original signal. Self-recovery schemes for audio, image, or video signals have been proposed in the literature in recent years. In general, the strategies deal with modifying the insertion domain or improving the compression process required for watermark insertion. Some relevant proposals that insert the watermark in the spatial domain are [10; 11; 12; 13]; similarly, the use of the frequency domain as the insertion space was reported in [14; 15; 16]. The use of the two domains, spatial and temporal, has also been explored by utilizing video signal as the host in [17; 18]. Reference [19] proposed a scheme for video signals in the DCT domain, and it resists MPEG attacks. However, self-recovering schemes are limited in their additional payload to the compressed version of the host signal that is used as a watermark. If additional information is inserted, the distortion caused can be prohibitive for real-world applications.