Secure single-sensor digital camera

Introduction: Digital cameras are the most popular image acquisition device. Images taken with a digital camera are usually downloaded on a personal computer (PC) where they are watermarked [1] for copyright protection and ownership authentication prior to storage and re-distribution. However, this way provides a space that attackers can utilise to violate intellectual property and ownership rights [1, 2]. To overcome the problem, secure digital cameras attempt to eliminate the security gap between image acquisition and processing at the companion device by implementing real-time watermarking solutions in the camera hardware. Existing solutions can watermark the colour image in a component-wise manner [1] or by altering the discrete cosine transform (DCT) coefficients of the host image [2]. However, most digital cameras capture colour information of the true visual scene using a colour filter array (CFA) placed on top of a single image sensor and produce the full-colour image by demosaicking the grey-scale CFA sensor data [3, 4]. Since demosaicking introduces processing errors and triples the amount of input data, watermarking the demosaicked image can be counter-productive in terms of both the resultant image quality and the computational complexity.