Policy Enforcement for Rich Execution Environment Cryptographic Operations
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Solution Overview
Problem
Existing electronic devices face inefficiencies in managing cryptographic operations for DRM-protected content, particularly in memory handling and authorization processes, which require real-time connections between different execution environments and involve unnecessary data copying and buffering.
Innovation Solution
The Content Protection Policy (CPP) infrastructure allows the Rich Execution Environment (REE) to initiate and manage cryptographic operations, such as DRM decryption, while the Trusted Execution Environment (TEE) enforces policies, reducing the need for real-time connections and pre-allocated secure memory, and enabling dynamic memory allocation and operation within unsecured memory regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If real-time connection between TEE and REE is maintained for cryptographic operations, then security policy enforcement is ensured, but system complexity and processing overhead increase
Solution Approach 1:
The system performs preliminary actions by pre-establishing secure memory regions with defined access policies before cryptographic operations begin. The TEE configures memory attributes and access rights in advance, allowing subsequent REE-initiated operations to proceed without real-time TEE intervention for each memory access, thus reducing processing overhead while maintaining security.
Solution Approach 2:
The patent introduces an intermediary mechanism where the TEE establishes secure memory regions that act as intermediaries between the REE and secure cryptographic operations. Once these regions are configured, the REE can directly access them without continuous TEE mediation, reducing system complexity while the TEE retains ultimate control through initial configuration and policy enforcement.
2Reliability
If pre-allocated secure memory is used for cryptographic operations, then security is maintained, but memory efficiency and flexibility are reduced
Solution Approach 1:
The system implements dynamic memory management where secure memory regions are not permanently reserved but are allocated and configured on-demand. The TEE can dynamically create, modify, and remove secure memory regions based on the specific cryptographic operations required, allowing the REE to utilize memory more efficiently while security is maintained through runtime policy enforcement.
Solution Approach 2:
The patent changes the parameter of memory allocation from static pre-allocation to dynamic configuration. Memory regions can be transformed between secure and non-secure states based on operational requirements, and their attributes (access rights, protection levels) can be modified during runtime, improving memory efficiency while maintaining security through controlled parameter changes.
3Reliability
If data copying and buffering between TEE and REE is performed, then data security is ensured, but processing speed and operational efficiency are reduced
Solution Approach 1:
The patent extracts the security enforcement function from the data copying process itself. Instead of copying data through multiple buffers with security checks at each stage, the system allows the REE to access secure memory regions directly, with security policies enforced at the memory access level rather than through data copying mechanisms, thereby eliminating unnecessary buffering overhead.
Solution Approach 2:
The system uses virtual memory copying techniques where the REE can access secure data through virtual addresses that map to physical secure memory regions. This creates the appearance of data copying for security purposes while actually enabling direct access to the underlying secure memory, maintaining security without the performance penalty of physical data copying and buffering.
Data Source
AI summary
Device, system, and method of policy enforcement for rich execution environment. An electronic device includes a Trusted Execution Environment (TEE), a Rich Execution Environment (REE), and a hardware-based secure sub-system which includes a cryptographic engine. The REE includes a cryptographic driver configured to initiate a request for TEE authorization to perform a particular cryptographic operation by the cryptographic engine on a data-item that is stored in a memory region that is accessible by the REE. The TEE includes a policies manager to determine whether the request from the REE is approved or rejected, and if approved, to inject data-items into the secure sub-system to enable performance of the requested cryptographic operation by the cryptographic engine.