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2.2 Watermark Verification\r\nA watermarking scheme with detection consists of four polynomial-time algorithms\r\nGENKEY , GENW, embed function E, and detection function D.\r\nGENKEY and GENW are probabilistic and generate a key-pair (kemb, kdet) and\r\na watermark W. The algorithm E(I,W, kemb) imperceptibly embeds the watermark\r\nW into the cover-data I, using the key kemb. This results in stego-data IW\r\n(watermarked version of I). The algorithm D(I_,W, I, kdet) returns a boolean\r\nvalue, which states whether the cover data I_ contains the watermark W relative\r\nto the reference data I, using key kdet. A symmetric watermarking scheme\r\nneeds the same key kw) for detection as for embedding. Unkeyed watermarking\r\nschemes need no key for embedding or detection. Watermarking schemes whose\r\ndetect algorithms D do not require the input of reference data I are called blind,\r\nin contrast to non-blind schemes.\r\nWe can consider three watermark mechanisms for digital data D_, which\r\nare the (1) watermark(W) casting mechanism, (2) signature(D∗ signing\r\nmechanism, and (3) signature hiding and verification mechanism. In this Fig. 2,\r\nwe can easily understand two mechanisms among these three mechanism. We\r\ncan embed some mark W on digital data D_. So, it is the common watermark\r\nembedding and verification(recovery) mechanism(mark casting mechanism).\r\nThe other one is the cryptographic mechanism as we can attach digital signature\r\nD∗ on digital data D_ for authentication(signing mechanism). From these two\r\nmechanism, we can consider new hybrid mechanism(signature hiding and veri-\r\nfication mechanism). As we can think signature as its watermark information,\r\nwe can hide this signature on its digital data for verifying ownership and\r\nauthentication. So, we can construct hybrid mechanism on digital watermark\r\nverification and authentication system. |
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发表于 2005-05-22 08:41
