Secure Key-Handling Unit for Trusted Platform Node Access
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Solution Overview
Problem
Current trusted platforms, relying on conventional Operating Systems, are insufficiently protected against subversion, limiting the effectiveness of integrity measurements and key management due to the lack of trustworthiness in OS's ability to reliably measure and store metrics in Platform Configuration Registers (PCRs).
Innovation Solution
A computing platform with a secure key-handling unit that stores a storage root key and allows for the dynamic selection of a non-leaf node as the current decryption-root key, which can be changed under specific conditions, such as receipt of an authorization value from a protected process, enabling secure access to a hierarchy of encrypted keys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional Operating Systems are used to manage key hierarchy, then ease of operation is improved, but security and reliability deteriorate due to lack of protection against subversion
Solution Approach 1:
The system segments key management functionality into two parts: conventional OS-level operations for ease of use, and a protected process with isolated memory space for security-critical operations. The protected process acts as an intermediary that handles sensitive key hierarchy operations while being isolated from potential subversion in the conventional OS.
Solution Approach 2:
A protected process serves as an intermediary between the conventional OS and the key hierarchy. This intermediary operates in a protected memory space, receiving requests from the OS, performing secure operations, and returning results. This mediator approach allows the system to maintain ease of operation through the OS interface while ensuring reliability through the protected process.
2Adaptability or versatility
If integrity measurements are stored in PCRs after OS loading, then adaptability is improved, but measurement precision and trustworthiness deteriorate due to OS subversion risks
Solution Approach 1:
The system performs integrity measurements in a protected process before trusting the OS completely. By establishing a measured and protected state early in the boot process, the system creates a foundation of trust that can then adapt to OS operations. Subsequent measurements are performed within this protected context, ensuring their precision and trustworthiness.
Solution Approach 2:
The system dynamically transitions between unprotected and protected states. Initially, measurements are taken in a protected process isolated from the OS. As the system boots and verifies integrity, it dynamically adjusts the level of protection, allowing measured processes to operate with appropriate trust while maintaining protection against unverified code.
3Reliability
If constant authorization checks are implemented for key access, then security is improved, but productivity deteriorates due to frequent verification overhead
Solution Approach 1:
Authorization is performed preliminarily when processes are loaded into the protected process's memory space. Once a process is verified and loaded, it can access the key hierarchy without repeated authorization checks. This preliminary verification approach maintains security by ensuring only authorized processes can be loaded, while improving productivity by eliminating continuous verification overhead during operation.
4Reliability
If the entire key hierarchy is stored in protected memory, then security is improved, but device complexity increases
Solution Approach 1:
The system extracts only the critical security functions and key hierarchy into a protected process with isolated memory space, while leaving the rest of the OS to operate conventionally. This extraction approach provides security for the most sensitive operations without requiring the entire system to be redesigned with complex protection mechanisms, thus limiting the increase in device complexity to only the necessary protected components.
Data Source
AI summary
Processing apparatus, such as a trusted platform, is provided with an access-control arrangement for handling a tree-structured hierarchy such as a key hierarchy. The access-control arrangement only permits access to a particular node of the hierarchy upon receiving a reliable indication that a mechanism expected to resist subversion will attempt to enforce appropriate access restrictions on that node. Such a mechanism is, for example, a protected process executing in a benign environment in the apparatus. The indication that the mechanism is in place is provided by a trusted source, such as a hardware root of trust responsible for initiating the mechanism. Access to the particular node opens the way to revealing that node, and any descendants, to the protected process.