The PTO issues new patents on Tuesdays. Both of this week's Spotlight Patents concern aspects of conditional access systems typically employed in cable and IPTV systems. Assigned to the ETRI (KR), the first patent addresses techniques for a downloadable conditional access system. Assigned to Nagravision, the second patent addresses techniques for traceable decryption of bandwidth-efficient broadcast of encrypted messages and security module revocation.
8,549,302, "Downloadable conditional access system, channel setting method and message structure for 2-way communication between terminal and authentication server in the downloadable conditional access system," assigned to the Electronics and Telecommunications Research Institute (KR)
Provided are a Downloadable Conditional Access System (DCAS), and a channel setting method and a message format for a 2-way communication between a terminal and an authentication server in the DCAS. The DCAS may include: a verification unit to verify an electronic signature and an integrity with respect to a message received from the authentication server; an extraction unit to extract network access information of the authentication server from the message in which the electronic signature and the integrity are verified; and a channel setting unit to set a communication channel with the authentication server based on the extracted network access information.
8,548,167, "System for traceable decryption of bandwidth-efficient broadcast of encrypted messages and security module revocation method used for securing broadcasted messages," assigned to Nagravision S.A. (CH).
The present invention makes use of techniques such as those described by Boneh and Franklin to allow for the realization of a pseudo-asymmetric encryption scheme whereby one public encryption corresponds to a plurality of private decryption keys. This scheme therefore provides a solution to the problem of inefficient use of bandwidth in asymmetrical encryption schemes which inherently require that a plurality of encryptions of data be broadcast to a plurality of receivers. The invention further ensures that the advantage of traceability, typical found in asymmetric encryption schemes, is maintained due to the characteristic that each receiver uses a unique traceable decryption key. The traceability thus achieved by the present invention allows for the revocation of a security module which has been involved in the abusive use of conditional access data, particularly by means of clones of security modules whose security has been compromised.