In this article, we focus on the complementary role of watermarking with respect to medical information security (integrity, authenticity ) and management We review sample cases where watermarking has been deployed, we conclude that watermarking has found a niche role in healthcare systems, as an instrument for protection of medical information, for secure sharing and handling of medical images The concern of medical experts on the preservation of documents diagnostic integrity remains paramount

A Review of Image Watermarking Applications in Healthcare

Authenticating medical images using watermarking techniques has become a very popular area of research, and some works in this area have been reported worldwide recently. Besides authentication, many data-hiding techniques have been proposed to conceal patient’s data into medical images aiming to reduce the cost needed to store data and the time needed to transmit data when required. In this paper, we present a new hybrid watermarking scheme for DICOM images. In our scheme, two well-known techniques are combined to gain the advantages of both and fulfill the requirements of authentication and data hiding. The scheme divides the images into two parts, the region of interest (ROI) and the region of non-interest (RONI). Patient’s data are embedded into ROI using a reversible technique based on difference expansion, while tamper detection and recovery data are embedded into RONI using a robust technique based on discrete wavelet transform. The experimental results show the ability of hiding patient’s data with a very good visual quality, while ROI, the most important area for diagnosis, is retrieved exactly at the receiver side. The scheme also shows some robustness against certain levels of salt and pepper and cropping noise.

Authentication and Data Hiding Using a Hybrid ROI-Based Watermarking Scheme for DICOM Images

Multiple watermarking based techniques are receiving more attention in recent times for its wide variety of applications in different fields. To protect the copyright ownership and validate the authenticity of multiple owners, in this paper a color multiple watermarking method based on DCT (Discrete Cosine Transform) and repetition code is proposed and simulated. Initially, green and blue components of color host image are selected for inserting multiple watermarks. Then, each green and blue component of the image is decomposed into non overlapping blocks and subsequently DCT is employed on each block. In this technique, a binary bit of watermark is embedded into green/blue component’s transformed block by modifying some middle significant AC coefficients using repetition code. During multiple watermarks embedding in green and blue components of the proposed method, DC and some higher AC coefficients are kept intact after zigzag scanning of each DCT block to ensure the imperceptibility of the watermarked host image. The proposed scheme is experimented to establish the validity by extracting adequate multiple watermark data from the restructured cover image after applying common geometric transformation attacks (like rotation, cropping, scaling and deletion of lines/columns etc.), common enhancement technique attacks (like lowpass filtering, histogram equalization, sharpening, gamma correction, noise addition etc.) and JPEG compression attacks.

A blind DCT based color watermarking algorithm for embedding multiple watermarks

http://lms.ctl.cyut.edu.tw/sysdata/8/21108/doc/d7b84166985e286b/attach/905835.pdf

Medical image security and EPR hiding using Shamir's secret sharing scheme

http://www.isical.ac.in/~malay/Papers/CMPB-PP-2013.pdf

Effective management of medical information through ROI-lossless fragile image watermarking technique

Medical images in digital form must be stored in a secure way to preserve stringent image quality standards and prevent unauthorised disclosure of 
patient data. This paper proposes a multiple watermarking method to serve these purposes. A multiple watermark consists of an annotation part and a fragile part. Encrypted patient data can be embedded in 
an annotation watermark, and tampering can be detected using a fragile watermark. The embedded patient data not only save storage space, it also offers 
privacy and security. We also evaluate the images’ visual quality after watermark embedding and the effectiveness of locating tampered regions.

/pdf/multiple-watermark-method-for-privacy-control-and-tamper-2i5te1rusf.pdf

Multiple Watermark Method for Privacy Control and Tamper Detection in Medical Images.

The essential performance metrics of a robust watermark include robustness, imperceptibility, watermark capacity and security. In addition, computational cost is important for practicality. Wavelet-based image watermarking methods exploit the frequency information and spatial information of the transformed data in multiple resolutions to gain robustness. Although the Human Visual System (HVS) model offers imperceptibility in wavelet-based watermarking, it suffers high computational cost. In this paper, we examine embedding strength determined by a HVS model, a constant, and a simplified technique. The proposed simplified embedding technique significantly reduces embedding time while preserving the performance of imperceptibility and robustness. The fast embedding technique exploits implicit features of discrete wavelet transform (DWT) sub-bands, i.e. the luminosity information in the low pass band, and the edge information in the high pass bands. It achieves embedding speed comparable to a constant energy embedding process. Robustness is demonstrated with a few conventional attacks, e.g. JPEG compression, Gaussian noise insertion, image cropping, contrast adjustment, median filtering, and global geometrical distortion. Experimental visual quality is measured in Weighted-Peak Signal to Noise Ratio (W-PSNR) for high accuracy. Robustness and imperceptibility of HVS-based embedding could be trade-off with computational simplicity of a fast embedding technique.

Performance factors analysis of a wavelet-based watermarking method

We report continuing investigations into practical applications of the AC Josephson effect as the basis for a voltage-tunable radio-frequency oscillator. We have previously demonstrated experimentally that useful power levels (10 s of nW) and linewidths of a few kHz can be achieved in the heterodyne output from a high-temperature-superconducting resistive SQUID (HTS-RSQUID) operating in the frequency range 1-50 MHz. Those results were achieved with 2-junction R-SQUIDs incorporating current-biased shunt resistors of a few micro-ohms. We have now modified the fabrication procedures, and adjusted the shunt resistors and bias current values so that higher frequencies can be achieved. The Josephson junctions are of step-edge type, rather than the bi-crystal type used in our earlier work. The step-edge technique permits much more flexibility in the geometrical lay-out and utilizes the more cost-effective single-crystal MgO substrates. In the present paper, we report numerical simulations and experimental measurements on these devices in the frequency range up to 2 GHz.

/pdf/simulation-and-measurement-of-hts-josephson-heterodyne-55vginjklw.pdf

Simulation and Measurement of HTS Josephson Heterodyne Oscillator

Robust watermarks are suitable for copyright protection in a DRM scenario. On the other hand, fragile watermarks are good for tamper detection applications. Semi fragile watermarks possess some properties of both robust and fragile watermarks at a moderate level. The need for semi fragile watermarks arises from the requirements of content authentication where the watermark must highlight malicious attacks while tolerating legitimate changes that do not alter the content severely. Very few watermarking scheme has both self authentication and self recovery features. We developed and evaluated a semi fragile watermarking scheme that offers these features. The scheme embeds a downscaled version of an image into the image’s discrete wavelet transform subbands. Our scheme provides content authentication by allowing high quality JPEG compression, minor local distortion, and minimal noise insertion. Other changes such as histogram equalisation, cropping, rotation, and mean filtering are classified as malicious attacks because it affects the visual quality of the image. The scheme is practical because it does not require a reference image during content authentication. Tampered regions can be located correctly, and its original content can be recovered. The watermark information is secured by a secret key that randomises the watermark pixel positions. The single transform, correlator detector, and down-scaled processing spaces of the scheme offer low computational cost.

Semi fragile watermark with self authentication and self recovery

To enable copyright protection and authentication, robust digital watermark can be embedded into multimedia contents imperceptibly. However, geometric distortions pose a significant threat to robust image watermarking because it can desynchronize the watermark information while preserving the visual quality. To overcome this, we developed an invariant domain with three transforms; Fast Fourier Transform (FFT), Log-Polar Mapping (LPM), and Dual Tree-Complex Wavelet Transform (DT-CWT). Shift invariance is obtained using FFT. Rotation and scaling invariance are achieved by taking the DT-CWT of a LPM output. Unlike most invariant schemes, our method eliminates explicit re-synchronization. The method resists geometric distortions at both global and local scales. It is also robust against JPEG compression and common image processing. In addition, it exploits perceptual masking property of the DT-CWT subbands, and its watermark detection step does not require the cover image. Experiment on a large set of natural images shows the robustness of the new scheme.

Jiang Du

Papers

Multiple Watermark Method for Privacy Control and Tamper Detection in Medical Images.

Performance factors analysis of a wavelet-based watermarking method

Simulation and Measurement of HTS Josephson Heterodyne Oscillator

Semi fragile watermark with self authentication and self recovery

Geometric Invariant Domain for Image Watermarking