Secure Authentication Channel for CI+ Decryption Bandwidth
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Solution Overview
Problem
The existing Common Interface Plus (CI+) interface requires significant bandwidth to send two complete transport streams between the set-top box and the Conditional Access Module (CICAM), making it inconvenient for decryption with multiple tuners.
Innovation Solution
A secure authentication channel (SAC) is generated between the CICAM and the set-top box, allowing only the control word and usage rules to be transmitted, reducing the data passed over the interface, and enabling efficient decryption of multiple transport streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two complete transport streams are sent over the interface between the set-top box and the CICAM, then decryption can be performed, but the bandwidth required becomes excessively large
Solution Approach 1:
The patent extracts only the essential decryption elements (control words and usage rules) from the complete transport stream and transmits them separately over the interface. This separates the bulk encrypted content (processed locally) from the critical access control data (transmitted over interface), thereby reducing interface bandwidth requirements while maintaining decryption capability.
Solution Approach 2:
The patent segments the transport stream processing into two parts: encrypted content processing (done locally in the set-top box) and control word generation (done in the CICAM). By dividing the decryption process into these segments and transmitting only the control words over the interface, the bandwidth burden is significantly reduced.
2Productivity
If the interface bandwidth is reduced to enable multiple tuner decryption, then the amount of data transmitted decreases, but ensuring security and access control becomes more challenging
Solution Approach 1:
The patent introduces a secure authentication channel as an intermediary mechanism between the set-top box and CICAM. This dedicated secure channel transmits control words and usage rules with enhanced protection, ensuring that even with reduced data transmission, security and access control are maintained through specialized security protocols.
3Quantity of substance
If only control words and usage rules are transmitted over the interface, then bandwidth usage is reduced, but the complexity of managing secure authentication increases
Solution Approach 1:
The patent implements a universal secure authentication channel that handles multiple functions: control word transmission, usage rule distribution, and security management. This multi-functional channel consolidates what could be multiple separate complex systems into a single standardized interface, reducing overall system complexity despite the specialized security requirements.
Data Source
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AI summary
A module configured in operation to connect to a host, the module comprising: a decryptor operable to decrypt an encrypted transport stream received from the host, the transport stream containing content data and a decryption seed; a decryption key generator operable to extract the decryption seed from the transport stream and to generate a decryption key from said decryption key seed; and a secure channel generator operable to generate a secure channel between the module and the host, whereby the secure channel generator is further operable to provide the generated decryption key to the host over the secure channel.