Separating Content Keys and Policy for Secure Decryption
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Solution Overview
Problem
Current cryptographic key techniques are vulnerable to attacks, where a single successful breach can leave large amounts of digital content unprotected, posing a risk for content owners and distributors.
Innovation Solution
Implementing a system that separates keys and policies for content consumption, where a leaf license includes a content key for decryption, and root policy addenda define permissible actions, ensuring that only authorized actions can be performed on encrypted content by using a device-specific key to decrypt the content key.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single cryptographic key is used to protect content, then content can be decrypted and accessed, but if the key is broken, a large amount of content becomes unprotected
Solution Approach 1:
The patent segments the cryptographic protection system into multiple independent components: content keys for individual content items and a separate device key for the device. This segmentation ensures that compromising one component does not automatically compromise all content, as each content key is independently protected. The root policy addenda further segment the control mechanism, separating authorization logic from key storage.
Solution Approach 2:
The patent introduces root policy addenda as an intermediary layer between the device key and content keys. This intermediary contains authorization policies that must be satisfied before a device key can access content keys, adding an additional security layer that prevents direct access even if the device key is compromised. The intermediary validates whether the device is authorized to access specific content based on policy rules.
2Ease of operation
If content keys are stored with licenses, then content can be decrypted, but the license becomes a target for attacks that could expose both content and keys
Solution Approach 1:
The patent extracts the content keys from the license structure and stores them separately in a protected key store. The license now contains only metadata and authorization information, while the actual decryption keys are stored in a secure, isolated key store that requires additional authorization through root policy addenda. This extraction reduces the attack surface of the license file, as it no longer contains the valuable content keys that attackers seek.
3Adaptability or versatility
If device keys are used to decrypt content keys, then content access is enabled, but compromise of the device key could lead to unauthorized content access
Solution Approach 1:
The patent implements preliminary action by requiring root policy addenda to be evaluated and authorized before device keys can access content keys. The system pre-establishes authorization policies in the root policy addenda that define under what conditions a device key may access specific content keys. This preliminary authorization check ensures that even if a device key is compromised, it cannot access content keys unless the pre-established policies permit it, thereby maintaining security against device key compromise.
Data Source
AI summary
In accordance with one or more aspects of the separating keys and policy for consuming content, content has a corresponding leaf license, and the leaf license has one or more associated root policy addenda. Each root policy addenda includes policy identifying when it is permissible to decrypt and consume the content, but excludes a content key to decrypt the content. The content can be decrypted and consumed only if the policy identifies that it is permissible to decrypt and consume the content.