Text Watermarks Research Articles

A novel chaotic IWT-LSB blind watermarking approach with flexible capacity for secure transmission of authenticated medical images

Nowadays, secure medical data transmission is an essential issue in telemedicine through unsecured channels. Watermarking methods are widely used to provide optimal security for medical image transmission. In this method, a secure and blind watermarking algorithm based on Integer Wavelet Transform (IWT), Least Significant Bit (LSB), and chaotic sequences (ILC) with a high capacity for grayscale medical and non-medical images is ILC. In this scheme, the high-level security is achieved by chaotic sequences that are applied for watermark encryption and determining the location of host blocks and host coefficients in the embedding process. At first, the cover medical image is divided into two distinct parts: the region of interest (ROI) and the region of non-interest (RONI) areas. Due to the high sensitivity of the ROI data in disease diagnosis, no embedding is done in this area. An ROI integrity check data (ICR), produced by some significant features from ROI, to detect tampered blocks inside this area. The main watermark, which is the encryption of ICR along with the patient’s personal and medical information, is embedded in the middle-frequency at the first and second levels of IWT sub-bands. Furthermore, to verify the watermark, integrity check data (ICW) is produced and sent along with other essential data to the receiver. For identifying authentication purposes, the physician’s signature is embedded at the third level (LL3) sub-band of IWT which has the highest energy and robustness. Moreover, the algorithm is flexible for using different sizes of text watermarks and it guarantees a high payload capacity. It is noteworthy the maximum lengths of text watermarks used in the method for 512×512 and 1024×1024 images are 47,784 and 164,620 bits, respectively. Although the size of the embedded watermark increases with the size of the ROI area, the image transparency remains almost constant and also the watermark is extracted with a bit error rate of zero. By doing various analyses, the experimental results represent superior imperceptibility by an average PSNR value of 75 dB. This method provides high imperceptibility and robustness against various attacks compared with state-of-the-art algorithms.

A proposed secure multiple watermarking technique based on DWT, DCT and SVD for application in medicine

In this paper, an algorithm for multiple watermarking based on discrete wavelet transforms (DWT), discrete cosine transform (DCT) and singular value decomposition (SVD) has been proposed for healthcare applications. For identity authentication purpose, the proposed method uses three watermarks in the form of medical Lump image watermark, the doctor signature/identification code and diagnostic information of the patient as the text watermarks. In order to improve the robustness performance of the image watermark, Back Propagation Neural Network (BPNN) is applied to the extracted image watermark to reduce the noise effects on the watermarked image. The security of the image watermark is also enhanced by using Arnold transform before embedding into the cover. Further, the symptom and signature text watermarks are also encoded by lossless arithmetic compression technique and Hamming error correction code respectively. The compressed and encoded text watermark is then embedded into the cover image. Experimental results are obtained by varying the gain factor, different sizes of text watermarks and the different cover image modalities. The results are provided to illustrate that the proposed method is able to withstand a different of signal processing attacks and has been found to be giving excellent performance for robustness, imperceptibility, capacity and security simultaneously. The robustness performance of the method is also compared with other reported techniques. Finally, the visual quality of the watermarked image is evaluated by the subjective method also. This shows that the visual quality of the watermarked images is acceptable for diagnosis at different gain factors. Therefore the proposed method may find potential application in prevention of patient identity theft in healthcare applications.

Robust and Imperceptible Spread-Spectrum Watermarking for Telemedicine Applications

This paper presents a new robust and secure digital watermarking scheme for its potential application in Telemedicine. The algorithm embeds medical text watermarks such as patient’s identity, image identity code and doctor’s identity into selected sub-band discrete wavelet transform (DWT) coefficients of the cover medical image using spread-spectrum technique. In the embedding process, the cover image is decomposed up to third level DWT coefficients. Three different text watermarks are embedded into the selected horizontal and vertical sub band DWT coefficients of the first, second and third level respectively. Selection of these coefficients for embedding purpose is based on threshold criteria defined in this paper. Robustness of the proposed watermarking scheme is further enhanced by applying error correcting code to the ASCII representation of the text watermark and the encoded text watermark is finally embedded into the cover medical image. It is found that the proposed scheme correctly extracts the embedded watermarks without error and provides high degree robustness against numerous known attacks while maintaining the imperceptibility of watermarked image.