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This paper discusses a new approach to ‘watermarking’ digital signals using linear frequency modulated or ‘chirp’ coding. The principles underlying this approach are based on the use of a matched filter to provide a reconstruction of a chirped code that is uniquely robust, i.e. in the case of very low signal-to-noise ratios.
Chirp coding for authenticating data is generic in the sense that it can be used for a range of data types and applications (the authentication of speech and audio signals, for example). The theoretical and computational aspects of the matched filter and the properties of a chirp are revisited to provide the essential background to the method. Signal code generating schemes are then addressed and details of the coding and decoding techniques considered.
Blackledge, J.: Digital Watermarking and Self-Authentication using Chirp Coding. ISAST Transactions on Electronics and Signal Processing ISSN 1797-2329, issue: No. 1, Vol. 1, pages: 61-71, 2007. doi:10.21427/D77K88