Client control through content key format

摘要

Client control may be provided. First, content may be encrypted using an actual key. Then an identifier corresponding to a client device may be received and a transformation may be performed on the actual key and the identifier to produce a transmitted key. The transmitted key and the encrypted content may then be sent to the client device where it may be received. The client device may then receive the identifier corresponding to the client device and perform a reverse transformation on the transmitted key using the identifier to produce the actual key. The content may then be decrypted with the actual key.

主权项

1. An apparatus comprising:
a key validator configured to:
receive a transmitted key of a predetermined number of bytes, the transmitted key comprising an actual key in a first portion of the predetermined number of bytes, a usage count, and a check field in a second portion of the predetermined number of bytes,receive an identifier corresponding to a client device, the identifier comprising a system-on-chip identifier corresponding to the client device from a non-volatile memory within the client device, andperform a reverse transformation on the transmitted key using the identifier, wherein the key validator being configured to perform the reverse transformation comprises the key validator configured to:
verify the check field of the received transmitted key using the identifier to produce the actual key,clear, upon verifying the check field, the second portion of the predetermined number of bytes from in the transmitted key, andinitiate, in the cleared second portion, a key usage counter for the usage count; and a descrambler configured to:
receive the actual key from the key validator, anddecrypt content with the actual key, wherein the descrambler being configured to decrypt content comprises the descrambler being configured to;
set the key usage counter with the usage count produced by the reverse transformation,decrement the key usage counter each time a packet of the content is decrypted, andstop the content decryption when the key usage counter is zero.