18 March 2008 Forensic watermarking and bit-rate conversion of partially encrypted AAC bitstreams
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Abstract
Electronic Music Distribution (EMD) is undergoing two fundamental shifts. The delivery over wired broadband networks to personal computers is being replaced by delivery over heterogeneous wired and wireless networks, e.g. 3G and Wi-Fi, to a range of devices such as mobile phones, game consoles and in-car players. Moreover, restrictive DRM models bound to a limited set of devices are being replaced by flexible standards-based DRM schemes and increasingly forensic tracking technologies based on watermarking. Success of these EMD services will partially depend on scalable, low-complexity and bandwidth eficient content protection systems. In this context, we propose a new partial encryption scheme for Advanced Audio Coding (AAC) compressed audio which is particularly suitable for emerging EMD applications. The scheme encrypts only the scale-factor information in the AAC bitstream with an additive one-time-pad. This allows intermediate network nodes to transcode the bitstream to lower data rates without accessing the decryption keys, by increasing the scale-factor values and re-quantizing the corresponding spectral coeficients. Furthermore, the decryption key for each user is customized such that the decryption process imprints the audio with a unique forensic tracking watermark. This constitutes a secure, low-complexity watermark embedding process at the destination node, i.e. the player. As opposed to server-side embedding methods, the proposed scheme lowers the computational burden on servers and allows for network level bandwidth saving measures such as multi-casting and caching.
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Aweke Lemma, Aweke Lemma, Stefan Katzenbeisser, Stefan Katzenbeisser, Mehmet U. Celik, Mehmet U. Celik, S. Kirbiz, S. Kirbiz, } "Forensic watermarking and bit-rate conversion of partially encrypted AAC bitstreams", Proc. SPIE 6819, Security, Forensics, Steganography, and Watermarking of Multimedia Contents X, 681910 (18 March 2008); doi: 10.1117/12.765340; https://doi.org/10.1117/12.765340
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