초록 ▼

A watermarking procedure wherein each of a set of copies of the work has a slightly-modified form of a "baseline" watermark that is placed within a critical region of the data. The slight variations in the watermarks, however, are not perceptually visible and do not interfere with the work. If multi

A watermarking procedure wherein each of a set of copies of the work has a slightly-modified form of a "baseline" watermark that is placed within a critical region of the data. The slight variations in the watermarks, however, are not perceptually visible and do not interfere with the work. If multiple persons collude to attempt to create an "illicit" copy of the work (i.e., a copy without a watermark), however, at least one of the modified watermarks is present in the copy, thereby identifying both the illicit copy and the copier.

대표청구항 ▼

[ I claim:] [6.] An access control method, comprising the steps of:during a watermarking phase:generating a first digital string from an object sought to be protected to form a baseline watermark;generating a second digital string from given text;generating a watermark having a predetermined relatio

[ I claim:] [6.] An access control method, comprising the steps of:during a watermarking phase:generating a first digital string from an object sought to be protected to form a baseline watermark;generating a second digital string from given text;generating a watermark having a predetermined relationship to the first and second digital strings; andinserting the watermark into the object to protect access to the object;upon an access request:retrieving a derived watermark from the object to form a third digital string;generating a fourth digital string from the given text;correlating the third and fourth digital strings; andif the third and fourth digital strings have a predetermined correlation, authorizing access to the object.