FPGA implementation of image watermarking algorithm for a digital camera

In this paper, we present an FPGA implementation of a watermarking-based authentication algorithm for a digital camera to authenticate the snapshots in a manner that any changes of contents in the still image will be reflected in the embedded watermark. All components of a digital camera and a watermark algorithm are implemented in VHDL, simulated, synthesized and loaded into an FPGA device. To achieve the semifragile characteristics that survive a certain amount of compression, we employ the property of DCT coefficients quantization proposed by Lin and Chang (2000). The binary watermark bits are generated by exclusive ORing the binary logo with pseudo random binary sequence. Then watermark bits are embedded into the LSBs of DCT coefficients in the medium frequency range. The system consists of three main parts: image capture and LCD controller, watermark embedding part, and camera control unit. The FPGA implemented digital camera is tested to analyze the performance. It is shown that the watermarking algorithm can embed the watermark into the original image coming from a sensor much faster than the software implementation and the embedded image is easily transmitted to the PC by using the USB interface. The quality of the transmitted image is also comparable to the one implemented by a software algorithm.