Recording keys in a broadcast-encryption-based system

A system of obtaining forensic information for an anonymous attack of digital content without variations in a broadcast encryption system, comprising:

• a recording device for generating and outputting a recording of digital content, said device including a processor in communication with a storage medium and a memory module, said processor executing a program that:
• obtains a media key variant from a unified media key block;
• calculates a set of recording keys from a recording key table and said media key variant,
• generates a single title key,
• encrypts said digital content with said generated title key,
• encrypts said title key with each of the set of recording keys,
• records said encrypted title key in a header of said encrypted content, and
• using said encrypted title key for identifying, to a content protection licensing agency, one or more device keys being used by a server for an anonymous attack of said digital content.

A computer program product of obtaining forensic information for an anonymous attack of digital content without variations in a broadcast encryption system, said computer program product comprising a non-transitory computer usable medium having computer usable program code embodied therewith, said computer usable program code comprising computer usable program code configured to:

• receive digital content, a unified media key block, and a recording key table;
• calculate a set of recording keys from said recording key table using a media key variant calculated by said recording device from said unified media key block;
• generate a title key;
• encrypt said digital content with said generated title key;
• encrypt said generated title key with each one of said generated recording keys;
• add a header including said encrypted title key to said encrypted digital content;
• and
• store said encrypted digital content with said header on recordable media.

A method of obtaining forensic information for an anonymous attack of digital content without variations in a broadcast encryption system, comprising:

• receiving, by a playback media device, encrypted digital content, said playback device including a processor and being configured to play digital content recorded on media;
• wherein a recording media device previously:
• (i) received digital content, a unified media key block, and a recording key table, (ii) calculated a set of recording keys from said recording key table by using a media key variant from said unified media key block, (iii) generated a title key, (iv) encrypted said digital content with said generated title key, and (v) encrypted said generated title key with each one of said generated recording keys;
• determining, by said playback device, which of said encrypted title keys said playback device can decrypt;
• and
• using said encrypted title key to decrypt said digital content.