Content Key Revocation Through Periodic Access Re-Evaluation
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Solution Overview
Problem
Existing content protection systems, particularly in over-the-top (OTT) contexts, lack the ability to enforce access control with sufficient granularity, allowing keys to remain accessible indefinitely even after entitlement changes, leading to security vulnerabilities.
Innovation Solution
Implementing a system that regularly re-evaluates access conditions using trusted components, such as a trusted execution environment (TEE) and secure element (SE), to periodically check and enforce access rights, and if negative, prevents the use of content keys by clearing or encrypting them, ensuring secure key management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a key is transmitted in encrypted form and decryption is conditional on positive evaluation of access conditions, then content security is improved, but the key remains accessible indefinitely after initial decryption, reducing access control granularity
Solution Approach 1:
The patent implements periodic re-evaluation of access conditions at defined intervals (e.g., every 10 seconds) after initial key decryption. The conditional access module continuously monitors whether access conditions remain satisfied and can revoke key access periodically, transforming the static key access model into a dynamic periodic verification system that maintains security while enabling fine-grained access control.
2Measurement precision
If access conditions are re-evaluated periodically with fine granularity, then access control precision is improved, but system complexity increases due to continuous monitoring requirements
Solution Approach 1:
The patent establishes access conditions and evaluation criteria in advance before key decryption occurs. The conditional access module is pre-configured with the rules for periodic re-evaluation, eliminating the need for complex real-time decision logic during operation. This preliminary setup simplifies the ongoing verification process while maintaining high access control precision.
Solution Approach 2:
The system implements a feedback mechanism where the conditional access module continuously monitors access condition satisfaction and provides feedback to the key management system. When access conditions are no longer satisfied, the feedback triggers automatic key revocation. This closed-loop feedback system achieves precise access control through a relatively simple architectural pattern.
Data Source
AI summary
Devices, servers, systems and methods for content protection are provided. Disclosed embodiments improve temporal granularity of controlling access to the protected content and increase resilience against attacks attempting to prevent re-evaluation of conditions of access. Enforcement of re-evaluation may be based on the receipt and/or verification of tokens. In some embodiments, re-evaluation is enforced by periodically rendering content keys required for content decryption unuseable and/or clearing content keys already in use.