Enabling modification of control information, which controls the rights to content, where access to a key for decrypting the content requires a particular value that becomes modified when the control information is modified

摘要

A method of modifying a digital rights object including a first portion including a first key and a second portion including first control information for controlling the rights to content encrypted with a second key, the method including the steps of: a) calculating a first function from the first control information of the digital rights object; b) operating on the first key using the first function calculated in step a), to obtain the second key; c) modifying the first control information of the second portion to second control information; d) calculating a second function from the second control information of the digital rights object; and e) operating on the second key obtained in step b) using the second function calculated in step d), to obtain a third key for replacing the first key.