# Improved ECG Watermarking Technique Using Curvelet Transform
## 1 Introduction  
The health of a patient can be constantly be monitored with the help of medical devices and digital communication. The old patients can send their physiological signals to the hospitals to avoid a repeated visit to the hospital. However, this technology has some concern about the security and content of the information. If the patients broadcast their medical or private information on the Internet in that case security is an important issue. Information broadcast without security can be assessed, modified, hacked by some unauthorized user [1]. The privacy of the patient can be leaked and affects the ability to diagnose due to unauthorized access. United States was passed an Act in 1996 as the Health Insurance Portability and Accountability Act (HIPAA) to protect patient privacy (personal data). This act was instructed about security regarding the communicating and storing of confidential and private information [2]. One possible solution to secure and protect ECG information is using cryptography, in which the original signal is encrypted at the sender side and decrypted at the receiver end [3]. However, the protection is not robust against data piracy as well as changes the bio-medical information that hampers the ability to diagnose. In that sense, steganography and watermarking are the alternative approaches to secure the patient's data and information. A steganography approach [4; 5] provides the worthy embedding capacity, even though it preserves the invisibility of embedded data. However, the hidden information would fail to extract if marked signals were corrupted during the transmission. Thus, the watermark needs to resist against geometric operations like rotation, noise addition and cropping [6]. However limited embedded information size of the watermark can affect the imperceptibility of the watermarked signal. Nowadays, few authors have considered some method to hide patients' information as a piece of copyright information in electrocardiogram (ECG) signals, magnetic resonance imaging (MRI) and electroencephalogram (EEG) [7; 8]. The security of ECG signals using watermarking is still a developing area. Embedding a copyright message in an ECG signal is a sophisticated task, as the ability to diagnose the disease is dependent on the T and P waves of the QRS. Here QRS is the name for the combination of three of the graphical deflections seen on a typical electrocardiogram (EKG or ECG). Hence, the effects of data on T and P wave reduction are essential to cover the data in the ECG signal. Two watermarking approaches are used to embed a watermark in ECG signals. One is a spatial domain that modifies pixel intensities, and another one is the frequency domain, in which frequency is modified. In the spatial domain, a hidden message is embedded in the time domain of the original signal. A reversible ECG steganography method that is based on the coefficients of alignment and is resistant to image-processing attacks has been proposed by [PERSON] et al. [9]. Some authors have used discrete wavelets transform (DWT) to embed a watermark. [PERSON] et al. [10] presented a reversible ECG steganography using DWT. [PERSON] et al. [11] also used the wavelet transform and compression for hiding the copyright information into ECG signals. The combination of singular value decomposition (SVD) and DWT for hiding data in ECG signals has presented by [PERSON] et al. [12]. However, the wavelet transform is not able to represent the curvelet. The author [13; 12] also examined that the copyright information inserted in the High-High (HH) band offers the finest imperceptibility in DWT. However, the wavelet transforms not efficiently represent the curved lines in that existing DWT method due to the two-directional parameters such as scale and translation. Thus, some new curvelet transform is required to characterize 2-D or 3-D singularity. This transform having three parameters such as scale, translation and orientation. The three parameters are easy to represent curved lines.