Region-Based Watermarking of Biometric Images: Case Study in Fingerprint Images

In this paper, a novel scheme to watermark biometric images is proposed. It exploits the fact that biometric images, normally, have one region of interest, which represents the relevant part of information processable by most of the biometric-based identification/authentication systems. This proposed scheme consists of embedding the watermark into the region of interest only; thus, preserving the hidden data from the segmentation process that removes the useless background and keeps the region of interest unaltered; a process which can be used by an attacker as a cropping attack. Also, it provides more robustness and better imperceptibility of the embedded watermark. The proposed scheme is introduced into the optimum watermark detection in order to improve its performance. It is applied to fingerprint images, one of the most widely used and studied biometric data. The watermarking is assessed in two well-known transform domains: the discrete wavelet transform (DWT) and the discrete Fourier transform (DFT). The results obtained are very attractive and clearly show significant improvements when compared to the standard technique, which operates on the whole image. The results also reveal that the segmentation (cropping) attack does not affect the performance of the proposed technique, which also shows more robustness against other common attacks

Data Hiding for Securing Fingerprint Data Access

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Low order models for transonic afterbody aerodynamic characteristics

A key aspect in the preliminary design of new combat aircraft is the prediction of the afterbody and exhaust system aerodynamic drag. To meet the various operating conditions requirements for a multi-role vehicle the afterbody typically includes a variable geometry. Within the preliminary design context, this makes the aerodynamic performance prediction a difficult challenge. This research investigates reduced order models for prediction of the aerodynamic performance of axisymmetric transonic afterbody and nozzle systems for a range of aerodynamic conditions and geometric degrees of freedom. The aerodynamic performance metric of interest is afterbody drag coefficient (CD). Two reduced order models are investigated: artificial neural network and Gaussian process. The geometric variables include boattail closing angle, nozzle throat to exit area ratio and afterbody mean angle and the aerodynamic parameters are free-stream Mach number and nozzle pressure ratio. The results show that these types of reduced order models can be used for preliminary design aerodynamic performance prediction. The Gaussian process CD prediction is less accurate compared to the artificial neural network with the latter giving a prediction uncertainty of approximately ±0.01 in CD with a 2σ confidence level. The Gaussian process prediction uncertainty is approximately ±0.013 CD

Imperceptible non-blind watermarking and robustness against tone mapping operation attacks for high dynamic range images

High dynamic range (HDR) imaging has experienced a widespread during the recent years through various technologies, including social network applications, which necessitates robust watermarking schemes to protect the copyright and image authentication. As watermarked high dynamic range images need to be tone mapped for visualization purposes on the traditional low dynamic range displays, the associated tone mapping operators (TMOs) can be deemed inevitable attacks. In this paper, we show that the state-of-the-art non-blind watermarking algorithms are vulnerable to the TMO's attacks. Based on the results of our investigation, we propose an improved non-blind watermarking method and extensively evaluate with state-of-the-art non-blind watermarking schemes using a broad set of TMOs' attacks. The proposed method first divides a given host image into patches, each of which is then decomposed using the discrete wavelet transform (DWT). The high-high sub-band of DWT is then passed through chirp-z transformation, followed by QR decomposition. The proposed solution embeds the watermark into each of value of the upper triangular matrix obtained from QR decomposition. The efficiency of the proposed embedding scheme is evaluated by applying 14 different TMOs on the watermarked image and extracting the embedded watermark. The average of 100 normalized correlation values for each image is then taken into account as a criterion for comparison, which demonstrates the noticeably stronger performance of the proposed watermarking scheme with respect to the state-of-the-art non-blind watermarking alternatives