Real time watermarking to authenticate the WSQ bitstream

Fingerprints are becoming popular in automated systems and for IT system user authentication. They are unique to each person and are designed to allow instant establishment personal identity in real time application. Enhancing their security in terms of fidelity and integrity becomes paramount. Since fingerprint images are usually compressed using Wavelet-packet Scalar Quantization (WSQ) before they are transmitted over networks, in this paper, we apply a fragile watermarking algorithm operating directly in compressed domain for protecting the evidentiary integrity of the WSQ bitstream. This work is motivated by the results obtained in previous video watermarking methods working in variable length codeword (VLC) domain to provide real time detection. The principle of the method is based on mapping the codewords to the outside of the used codespace, the watermark is embedded into stream as forced bit errors. The developed algorithm achieves high capacity and preserves the file size of WSQ bitstream while maintaining high perceptible quality.