To protect access to information recorded on a light-readable disc, a
light-readable disc player provides the user with a unique key each time
the user attempts to play the disc. After the user communicates the unique
key to a transaction service and satisfies certain preconditions, such as
providing payment or account information, the transaction service provides
the user with an unlock key. The user communicates the unlock key to the
light-readable disc player, which plays the disc only if the user has
provided the correct unlock key.