Patent ID: 6785815
Filing Date: 2004-08-31
Classification: G06F,G06T,G11B,H04L,H04N

Abstract:
A method for protecting a digital file against unauthorized modification, the method including:encoding the file, the encoding including: inserting a first watermark into the file; inserting a plurality of signature-containing watermarks into the file, each signature-containing watermark containing the digital signature of at least a portion of the file; and decoding at least a portion of the encoded file, the decoding including: searching at least a portion of the encoded file for a first signature-containing watermark; if the first signature-containing watermark is found, retrieving a first digital signature from the first signature-containing watermark, and using the first digital signature to verify the authenticity of a portion of the encoded file to which the first digital signature corresponds; if the first signature-containing watermark is not found, searching the encoded file for the first watermark; if the first watermark is found, inhibiting at least one use of at least a portion of the file; if the first watermark is not found, permitting at least one use of at least a portion of the file; whereby the plurality of signature-containing watermarks are operable to facilitate detection of modifications to the encoded file, and the first watermark is operable to facilitate detection of removal of one or more of the signature-containing watermarks from the encoded file.