TEE-TPM Attestation Quotes Without EK Certificate Dependency
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Solution Overview
Problem
Existing TPM-based attestation methods require an Endorsement Key (EK) certificate, which may be difficult to obtain, leading to security vulnerabilities and complexity, especially in the absence of a TPM EK certificate, and lack flexibility in key usage and application-specific attestation.
Innovation Solution
Integrating a Trusted Execution Environment (TEE) with a TPM to generate attestation quotes using TPM Platform Configuration Registers (PCRs), enabling secure attestation without EK certificates and allowing flexible key usage and application-specific differentiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TPM-based key attestation is used to bind AK keys to TPM, then security and trustworthiness are improved, but device complexity and protocol implementation complexity increase significantly
Solution Approach 1:
The patent extracts the EK certificate verification step from the TPM attestation process. Instead of requiring the full TPM key attestation protocol with EK certificates, the invention uses a simplified approach where the TEE generates attestation quotes using only the TPM PCR values, eliminating the need for EK certificate management and verification
Solution Approach 2:
The patent segments the attestation process into two independent parts: (1) TPM measures platform state into PCR values, and (2) TEE generates signed attestation quotes using those PCR values. This segmentation allows the TEE to perform attestation without requiring the complex TPM key attestation infrastructure
2Reliability
If TPM EK certificate is required for attestation, then trust chain is established, but ease of operation deteriorates due to difficulty in obtaining EK certificates
Solution Approach 1:
The invention removes the EK certificate requirement from the attestation process. The TEE-based approach generates attestation quotes that do not depend on EK certificates, eliminating the operational difficulty of obtaining and managing these certificates while maintaining trust through the TEE's hardware-based security
Solution Approach 2:
The TEE acts as an intermediary between the TPM and the attestation verification process. Instead of directly using TPM EK certificates, the TEE receives PCR values from the TPM and generates its own signed attestation quotes, serving as a mediator that simplifies the trust establishment process
3Adaptability or versatility
If DAA group signature scheme is used for anonymous attestation, then privacy is preserved, but device complexity and number of steps increase
Solution Approach 1:
The patent uses TEE-based attestation quotes as a simplified alternative to DAA group signatures. The TEE generates cryptographic proofs that provide similar privacy and anonymity guarantees but through a more direct process that leverages existing TEE infrastructure rather than requiring DAA group joining and complex signature generation
4Reliability
If TPM is used for strong security with PCR measurements, then security is improved, but adaptability deteriorates due to limited key usage flexibility
Solution Approach 1:
The patent merges TPM's strong measurement capabilities with TEE's cryptographic flexibility. The TPM provides secure PCR measurements while the TEE performs the actual attestation signing, combining the strengths of both systems to achieve both security and adaptability
Solution Approach 2:
The TEE serves multiple functions: it receives PCR values from the TPM, generates attestation quotes, and provides flexible key usage for different applications. This multi-functionality allows the system to maintain TPM's security while adding the adaptability needed for various key usage scenarios
Data Source
AI summary
A method for enabling attestation of a platform comprising a Trusted Execution Environment, TEE, and a Trusted Platform Module, TPM is disclosed. The method is performed by the TEE and comprises: receiving, from an Application of the platform, a request for generation of an attestation quote, the request comprising a nonce, information on which PCR(s) to be used and information about Attestation Keys; establishing a connection to the TPM and obtaining from it at least one PCR value; generating an attestation quote based on the received nonce and the at least one PCR value; signing the attestation, and rendering the attestation quote available for the Application.