Cached Stream Encryption via Content-Derived Keys
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Solution Overview
Problem
Existing systems face challenges in enforcing restrictions and removing access to cached streamed content, particularly due to geographical licensing and copyright infringement issues, as DRM solutions require infrastructure changes and per-copy license fees, making them impractical for user-generated content services.
Innovation Solution
A method and system for protecting cached streams by creating an encryption key from a portion of the streamed content, which is stored along with the encrypted content, allowing the content server to control playback by regenerating the key upon request, even over unreliable protocols, and optionally using overlay keys for additional security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DRM software is used to protect cached content, then content protection and access control are improved, but infrastructure changes and per-copy license fees are required, making it impractical for user-generated content services
Solution Approach 1:
The system allows the cached content itself to serve as the encryption key (self-service), eliminating the need for external DRM infrastructure. The content's own data blocks are used to derive encryption keys, making the protection mechanism self-contained and suitable for user-generated content services without requiring per-copy license fees or complex infrastructure changes.
Solution Approach 2:
The patent uses temporary, content-specific encryption keys derived from the content itself rather than persistent DRM licenses. Each piece of cached content has its own ephemeral key that is discarded after use, eliminating the need for expensive, long-lived DRM license management infrastructure.
2Duration of action of stationary object
If content is cached locally to improve user experience, then playback continuity is improved, but control over access restrictions and copyright compliance deteriorates
Solution Approach 1:
The system performs preliminary encryption of cached content using keys derived from the content itself before storage. This preliminary action ensures that even though content is cached for continuous playback, it remains protected and accessible only through the derived key mechanism, maintaining both playback continuity and access control.
Solution Approach 2:
The patent changes the parameter of encryption key storage by not storing keys separately but instead deriving them from the content data itself. This parameter change ensures that cached content remains controllable through the derivation process, maintaining access control while enabling offline playback.
3Ease of operation
If encryption keys are stored with encrypted content, then decryption capability is improved, but security deteriorates if keys are compromised
Solution Approach 1:
The patent introduces content-derived data blocks as intermediaries between the encrypted content and the decryption process. Instead of storing keys directly with content, the system uses specific data blocks from the content itself as intermediaries to derive decryption keys, adding a layer of security while maintaining decryption capability.
Solution Approach 2:
The system segments the encryption key derivation process by using specific portions (data blocks) of the content to derive keys. This segmentation means that compromising one portion does not necessarily compromise the entire system, as different segments can be used for different encryption operations.
Data Source
AI summary
A system and method for protecting cached streamed data is disclosed. The method may include the steps of generating an encryption key from the streamed data itself, encrypting the streamed data stored in the storage device and requesting the portion of the streamed data from the content server again when later playback is desired so as to allow the content server to enforce access limitations or takedown policies relating to the streamed data. The method may also include procedures for handling key generation over reliable or unreliable protocols.