No abstract

In this paper, we review our past experience with security of copy control audio watermarks, particularly related to SDMI. We also classify and analyze attacks published in literature and propose a number of security enhancement techniques for copy control and other digital watermarking applications. One type of security measure is based on uncoordinated selection of hiding places between embedders and extractors, with statistical analysis of expected matches. This approach reduces the repeatability of attacks and opens up the possibility of system renewal.Other security measures are introduced, based on weak watermark detections, time diversity extraction, weight accumulation, soft decision decoding, and extraction expansion or focusing. Finally, we propose a number of methods to conceal watermark presence, location and properties using random embedding, extraction and reporting, and random host signal modification techniques design to counter differential analysis or scrambling attacks.

The Cross Interleaved Reed-Solomon Code (CIRC) used in CD-ROM for basic error correction/detection consists of two catenated, distance 5 Reed-Solomon codes. These two subcodes, which are called the C1 and C2 codes, have length 32 bytes and 28 bytes respectively. C1 and C2 can each correct any combination of t errors and e erasures in a given codeword, where t and e are jointly constrained by the inequality Specific values of t and e may be selected by a decoder when each C1 and C2 codeword is processed. The algorithm used to adaptively select the t and e values that apply when the C1 and C2 codes are jointly decoded is called the CIRC decoding strategy.

The new writable Compact Discs (CDs), such as the CD-R and Kodak's PhotoCD, are physically different from pressed CDs (such as CD-ROMs and Digital Audio Discs) and data marks are written on them with an entirely different physical process. Therefore, it is possible that the nature and statistical characteristics of errors that contaminate data carried by writable and pressed CDs will be quite different. This subject is addressed in an invited talk that is being presented at this conference. [1]