Guzin Ulutas

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

Medical applications such as telediagnosis require information exchange over insecure networks. Therefore, protection of the integrity and confidentiality of the medical images is an important issue. Another issue is to store electronic patient record (EPR) in the medical image by steganographic or watermarking techniques. Studies reported in the literature deal with some of these issues but not all of them are satisfied in a single method. A medical image is distributed among a number of clinicians in telediagnosis and each one of them has all the information about the patients medical condition. However, disclosing all the information about an important patients medical condition to each of the clinicians is a security issue. This paper proposes a (k, n) secret sharing scheme which shares medical images among a health team of n clinicians such that at least k of them must gather to reveal the medical image to diagnose. Shamirs secret sharing scheme is used to address all of these security issues in one method. The proposed method can store longer EPR strings along with better authenticity and confidentiality properties while satisfying all the requirements as shown in the results.

Secret image sharing scheme with adaptive authentication strength

Transmission of secret messages or images over the Internet using Shamirs secret sharing scheme has become popular. Some researchers use steganography with Shamirs method to hide noise like share images into natural looking cover images to improve secrecy. Stego images are authenticated against accidental or deliberate changes before recovering the secret. Authentication by a parity bit stream calculated by a keyed hash of stego images is commonly used. Researchers aim to increase the number of authentication bits to improve the authentication strength of their methods. Eslami and Ahmadabadi (2011) proposed a method with dynamic embedding strategy in 2011. They use a concatenated string of four bits, two from the current and two from previous block, to authenticate individual blocks. Even though chaining performs block based authentication, it cannot detect individual fake stego blocks and cannot authenticate the rest of the stego image blocks if it faces a changed block. This paper proposes a new secret image sharing method by selecting the number of authentication bits proportional to block size, contrary to Eslami and Ahmadabadi (2011) method which uses four bits to authenticate blocks regardless of block size. The proposed method has improved authentication for increased block size and can authenticate individual stego blocks as well. It produces good quality stego images and can still authenticate the rest of the stego image even after an altered stego block is encountered as shown in the experimental results.

Copy-move forgery detection in images via 2D-Fourier Transform

Digital images have been widely used in many applications. However, digital image forgery has already become a serious problem due to the rapid development of powerful image editing software. One of the most commonly used forgery techniques is Copy-move forgery that copies a region of an image and pastes it on the other region in the same image. In recent years, most techniques aim to detect such tampering. Different feature extraction methods have been used to improve the capability of the detection algorithm. In this work, we used two dimensional Fourier Transform (2D-FT) to extract some features from the blocks. Predetermined number of Fourier coefficients hold information about the blocks. At the final stage, the similarity search between the adjacent feature vectors is performed to determine the forgery. Experimental results show that proposed method can detect the duplicated regions with high accuracy rate even if the image is distorted with blurring mask or it is compressed with different JPEG quality factors. The dimension of feature vector is also lower than the other methods in the literature. Thus, the method ensures the lower feature vector with high accuracy rates. The proposed method also detects multiple copy move forgery as shown in the results.

A new secret image sharing technique based on Asmuth Bloom's scheme

The Chinese Remainder Theorem (CRT) is used for secret sharing by both Mignotte and Asmuth Bloom in 1983. Then Shyu et al. used Mignottes scheme in the field of secret image sharing in 2008. However, their method use a Pseudo Random Number Generator (PRNG) with a seed to generate different pixel values for the consecutive secret pixels that have the same value. The need to distribute the seed and PRNG function to participants in order to reconstruct the secret image is a drawback of their method. A modified secret image sharing technique based on Asmuth Blooms secret sharing scheme is proposed in this paper. It does not require to distribute the seed or PRNG like Shyu et al.s technique. In addition, PRNG function is not used during decoding. Therefore, drawbacks in Shyu et al.s scheme is eliminated by the proposed method using Asmuth Blooms scheme as can be seen in the results.

Secret image sharing with reversible capabilities

Secret image sharing is a technique to share a secret image among n participants using Shamirs secret sharing scheme. Secret image is revealed if any k of the n shares is processed according to the scheme. Research reported in the literature is focused on improving known issues of the method. Reconstruction without distortion, reducing the size expansion of the share images, improving stego image quality and enhancing authentication ability of the method are some of the issues. Recovering cover images after the revealing procedure is an important issue. In 2009, Wu et al. proposed a technique based on reversible steganography to solve this problem. A location map is used to recover cover images, which needs extra information. The proposed method outlined in this paper does not need any information except shares to recover cover images. In addition, visual quality of the shares or the peak signal to noise ratio (PSNR) values of stego images are improved which is used to demonstrate the effectiveness of the method. Experimental results indicate a 3 dB PSNR improvement on the average compared to Wu et al.s method.

Secret image sharing with enhanced visual quality and authentication mechanism

Abstract Secret image sharing is a technique to share a secret image among n participants. Each participant has a meaningless, noise-like share. The image is revealed if any k of the shares are gathered. This scheme uses the polynomial based (k, n) secret sharing approach proposed by Shamir in 1979. In 2004, Lin and Tsai proposed a new secret image sharing method with steganography. Their scheme uses steganography to hide the shares into cover images. After this pioneering research, Yang et al. proposed a technique with enhanced stego image quality and better authentication ability in 2007. Wu et al. proposed another method to both decrease size expansion ratio of stego images and increase stego image quality by 0·5 dB compared to Yang et al.’s method in 2009. A new method with better authentication ability and stego image quality is proposed in this manuscript. More natural looking stego images of 43 dB peak signal-to-noise-ratio (PSNR) are generated by the proposed method exceeding Wu et al.’s method by 1·2 dB on the average. Also proposed method can detect fake stego blocks with probability 0·875 while other methods could detect with probability 0·5. The experimental results indicate enhanced authentication ability and visual quality compared to other methods.

Improvements in Geometry-Based Secret Image Sharing Approach with Steganography

Protection of the sensitive data is an important issue because of the fast development of applications that need exchange of the secret information over the Internet. Secret sharing is an idea proposed by Shamir and Blakley separately with different implementations in 1979. Lin and Tsai proposed a method that uses Steganography to create meaningful shares by using Shamirs secret sharing scheme in 2004. In recent years, researchers work to remove some of the weaknesses of this method. However, all of these methods need cover images four times bigger than the secret image. This arises two problems: increased storage and bandwidth need for shares. We used cover images with the same size as the secret image by using both Blakleys secret sharing approach and Steganography. Therefore, we achieved reduced storage and transmission bandwidth for shares. Besides, the proposed method creates meaningful shares by using Steganography instead of noise-like shares, different from other studies that use Blakleys approach.

(2,2)-Secret Sharing scheme with improved share randomness

Visual secret sharing (VSS) is a method to scatter a secret image into shares of random patterns that have to be stacked together to reconstruct the secret. Since each share is a random pattern of black and white pixels, it is not enough to rebuild the secret from just one share. Stacking two shares reconstructs the first secret whereas rotating the first share by 90deg counterclockwise and stacking reconstructs the second secret. A novel algorithm to create both shares from two secrets with improved randomness is proposed in this paper. Share creation algorithm selects extended patterns of random pixels to satisfy contrast requirements of both secrets reconstructed by normal and rotated stacking. Proposed method have desirable security properties because of the improved randomness of shares.

Frame duplication/mirroring detection method with binary features

Multimedia devices have become increasingly popular due to high quality and low cost products using advanced technology. These devices can capture multimedia files, which can be modified easily by video editing tools. One of the most frequently encountered forgery types in video forensics is the frame duplication (FD) forgery. Many methods have been proposed in the literature to deal with this type of forgery. These methods do not consider frame-mirroring (FM) attack which copy a sequence of frames and paste its mirrored versions somewhere else on the same video. A new FD/FM detection method is proposed in this work. The method extracts binary features from frames and determines the similarity among features. Peak-signal-to-noise ratio of the candidate frames is used to eliminate some of the large number of candidates to improve the detection of the forged frames. Experimental results show that the proposed method successfully detects FM/FD attacks and also yields better execution time and detection results compared to similar works reported in the literature.

A New Copy Move Forgery Detection Method Resistant to Object Removal with Uniform Background Forgery

Users transfer large number of images everyday over the Internet. Easy to use commercial and open source image editing tools have made intactness of images questionable. Passive methods have been proposed in the literature to determine authenticity of images. However, a specific type of forgery called “Object Removal with uniform Background forgery” becomes a problem for keypoint based methods in the literature. In this paper, we proposed an effective copy move forgery detection technique. The method uses AKAZE features and nonlinear scale space for detection of copied/pasted regions. The proposed method detects “Object Removal with uniform Background” and “Replication” types of forgeries with high precision compared to similar works. Experimental results also indicate that the method yields better discriminative capability compared to others even if forged image has been rotated, blurred, AWGN added, or compressed by JPEG to hide clues of forgery.