Time-Synchronized Key Transfer for Conditional Access
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Solution Overview
Problem
Conditional access systems face challenges in securely transferring decryption keys due to the ease of key discovery and sharing, particularly over the internet, which can lead to unauthorized access and revenue loss for content providers.
Innovation Solution
A method that requires security modules to send a verification message at a specific, pre-determined time to receive decryption keys, using a slave time counter synchronized with a reference time counter, ensuring only legitimate modules access the keys without affecting broadcast bandwidth and allowing for swift punitive actions against unauthorized use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If decryption keys are transferred securely to security modules, then unauthorized access is prevented, but key management complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-synchronizing time counters between the server and security modules before key transfer. The server defines a pre-determined calling time and calling time window for each receiver, and the security module's slave time counter is synchronized with the server's reference time counter in advance. This preliminary time synchronization enables the security module to autonomously determine when to request keys without complex real-time negotiation protocols.
Solution Approach 2:
The security module performs self-service by autonomously monitoring its own slave time counter and independently determining when to send verification messages based on the pre-determined calling time. The module automatically requests decryption keys from the server when the slave time equals the pre-determined calling time, eliminating the need for complex external scheduling or manual key management intervention.
2Reliability
If time-synchronized verification messages are required for key transfer, then key security is improved, but system operation complexity increases
Solution Approach 1:
The patent implements feedback through the time-synchronized verification mechanism. The server defines a pre-determined calling time and calling time window, and the security module provides feedback by sending a verification message when its slave time counter matches the pre-determined calling time. The server receives this verification message and confirms whether the time difference is within the acceptable window, creating a closed-loop feedback system that ensures secure key transfer while maintaining operational simplicity.
3Reliability
If decryption keys are frequently updated to prevent unauthorized access, then security is improved, but service disruption to authorized users increases
Solution Approach 1:
The patent applies dynamics by implementing a dynamic, on-demand key update mechanism triggered by time-synchronized verification messages. Instead of frequent periodic key updates that would disrupt service, the system updates keys dynamically when authorized security modules send verification messages at their pre-determined calling times. The server selectively transfers updated decryption keys only to modules that have successfully verified their time synchronization, allowing frequent key updates without penalizing authorized users.
Data Source
AI summary
The present invention may be deployed in a system for broadcast of conditional access content where it is desirable to detect and take action against receiver equipment which has been used in a control word sharing activity. By requiring that receiver equipment used in the system send a message to a broadcaster of conditional access content at a precise time, the invention provides a method for the server to detect receiver equipment involved in control word sharing activity and to inhibit that receiver's ability to further access the content.