Encrypted Title Key - Decryption Problems

Decryption Problems

Although the process of updating all the Title Keys for an application usually takes a very small amount of time (much less than a second), it is a critical time. If the device were to fail during the re-encryption process, the user's content might be lost. To reduce the risk of user loss, recording devices shall begin the reencryption process by renaming the old MKB to a temporary name before writing the new MKB. When the device completes the re-encryption process, it shall delete the temporary MKB. If any recorder discovers a temporary MKB on a piece of media, it is an indication that the encrypted Title Keys might be corrupted. The device shall perform one of the following protocols to recover the corrupted encrypted Title Keys. Which protocol is chosen depends on where the encrypted Title Keys are stored in the particular application. A device re-encrypting Title Keys as a normal result of updating a recordable MKB shall also use these same protocols.

These protocols are:

- Recovery Protocol When the Encrypted Title Keys are in a Separate File: In this case, the original recording device shall rename the old encrypted Title Keys to a defined temporary name before beginning to write the new encrypted Title Key File.

-Recovery Protocol When the Encrypted Title Keys are in the Content File: In the extreme case, each content file contains its own encrypted Title Key. In that case, it is not likely that there is a temporary version of the encrypted Title Keys.