# Reversible Data Hiding for DICOM Image Using Lifting and Companding
## 1 Introduction
However, it is seen that when the noise level is high and also affecting the major part of the image, the watermark is extracted wrongly. [PERSON] et al. [11] proposed the prediction-error expansion (PEE) technique for reversible watermarking, which embeds data uniformly. The scheme adaptively embeds one (1) or two (2) bits into the expandable pixel, based on local complexity. [PERSON] et al. [12] proposed a data hiding scheme that divides the host image into non-overlapping blocks. The scheme then embeds a watermark into the high-frequency wavelet coefficients of the above blocks. Authors argue that the scheme offers superior embedding capacity, and also the embedding distortion is maintained at a lesser level. [PERSON] et al. [13] present a reversible data hiding scheme for images without using the location map. The scheme uses prediction errors to embed data into the host image. A sorting technique is used to trace the prediction errors depending on the amount of its local variance. A reversible data embedding technique is proposed based on integer wavelet transform by [PERSON] et al. [14]. Data insertion is done by increasing the differences between one pixel and each of its three adjacent pixels. [PERSON] et al. [15] combine data hiding and image encryption to provide integrity/security in the cloud computing environment. The scheme uses block compressive sensing (BCS) technique to compress and encrypt the image. Then hidden data bits are embedded into the least significant nibble. The main feats of the scheme are improved compression, data-loss prevention, and embedding capacity. Most of the current solutions found in the literature compromise between the quality of the reproduced medical image and the numbers of effective watermark bits inserted, which are indicators of the strength of the authentication and originality mechanisms of solution. Moreover, due to the reduced number of effective inserted bits, the strength of the current solutions is highly vulnerable, and it can be broken with simple security algorithms or brute force attacks [16; 17]. Lastly, the schemes proposed in ([4; 9]) embed location map as side information for restoration of the host image. That ultimately reduces the effective embedding capacity of a scheme. [PERSON] et al. [18] proposed a prediction error expansion (PEE) based reversible watermarking technique where multiple histogram modification mechanism is used for better embedding performance. The method performs better than conventional PEE methods in terms of watermarked image quality, but it has limited embedding capacity. An improved implementation of pixel value ordering (IPVO)system is reported by [PERSON] et al [19]. The method has better embedding performance than other IPVO based reversible watermarking technique but the time and space complexity of the system are high. Recently, another improved pixel value ordering (IPVO) technique is proposed by [PERSON] et al [20]. The system uses dynamic IPVO technique which offers better embedding performance with good visual quality. To resolve the problems stated above, we proposed a novel reversible data hiding (watermarking) scheme that combining lifting based DWT with companding. The multi-resolution signal decomposition by wavelets transform reflects the anisotropic properties of the human visual system more exactly and helps to design data hiding scheme with high fidelity of the watermarked image [21; 22]. Because of the small changes in wavelet coefficients distort the image very less. Moreover, unlike previously proposed reversible watermarking techniques [9], this novel approach does not use any location map. So the scheme does not require to embed the location map in the host image that ultimately helps to achieve high fidelity and greater payload capacity of the watermarked image. The proposed data hiding encoder select all the coefficients of high-High (_HH_) frequency sub-band to embed the watermark bits, whereas the decoder selects the same frequency sub-band to retrieve the embedded watermark bits.