Boot Layer Integrity Verification Using OWF-Derived Symmetric Keys
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Solution Overview
Problem
Existing secure boot technologies, such as DICE, are limited by single measurement per boot layer, lack flexibility, and do not address error cases, particularly for devices with limited computational resources.
Innovation Solution
A method using a One-Way Function (OWF) to generate multiple result values, a unique device secret (UDS) for enhanced security, and symmetric key derivation to verify the integrity of each boot layer, ensuring efficient and flexible secure boot processes even in resource-constrained devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If asymmetric cryptography (e.g., UEFI Secure Boot) is used to verify software integrity during boot, then security is improved, but computational overhead increases making it unsuitable for devices with limited capabilities
Solution Approach 1:
The patent introduces a measurement value (hash) as an intermediary that represents the software state. Instead of directly verifying software using computationally intensive asymmetric cryptography, the system calculates a hash of the software and compares it against a reference value. This intermediary approach maintains security while dramatically reducing computational overhead for resource-constrained devices.
Solution Approach 2:
The patent creates a cryptographic copy (hash) of the software that can be verified without examining the original software directly. This hash copy serves as a lightweight representation that can be computed and verified with minimal computational resources, yet still provides strong integrity verification when compared against the reference hash value.
2Use of energy by moving object
If DICE is used for measured booting with single measurement per boot layer, then computational resources are saved, but flexibility and adaptability are reduced
Solution Approach 1:
The patent implements a universal measurement mechanism that can verify multiple boot layers and software components using the same hash-based approach. The measurement unit can calculate hashes for different types of software (firmware, operating system, applications) and at different boot stages, providing flexible and adaptable verification without requiring different cryptographic mechanisms for each case.
Solution Approach 2:
The patent enables dynamic measurement where the measurement unit can adaptively measure different software components based on system state and requirements. The reference value storage allows the system to dynamically update expected hash values for different software versions and configurations, providing flexibility while maintaining the computational efficiency of hash-based verification.
Data Source
Figure 1~3
AI summary
The present disclosure relates to a method and an apparatus for integrity testing of an executable function of a device. The disclosed method comprises several process steps. An OWF computational function, OWF_R, is executed during an operational startup of the device, particularly during an operating/application phase, wherein the executable function is divided into a plurality of boot layers, and wherein a unique device secret, UDS, is read from a storage device and used as input for the OWF computational function to generate two result values: 1) a first result value for a key chain, CDI0, and 2) a second result value for a secure boot verification chain, CDI_sec0.A symmetric authorization credential, CDI_K0, is determined by executing a key derivation function, KDF, in particular a DICE key derivation function, based on the second value, and the symmetric authorization credential is used to check the integrity of a first boot layer of the executable function by calculating an integrity check value, ICV_check, where the ICV_check is compared with an integrity reference value, ICV_ref, and if there is a match, another boot layer is loaded for testing; otherwise, an error result is provided for the integration check.