Persistent TPM Identifier and Key Pair Generation
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Solution Overview
Problem
The difficulty in establishing a persistent one-to-one mapping between a TPM identifier and the TPM itself due to privacy concerns, leading to the limitations of manufacturer-provisioned Endorsement Key (EK) and the impermanence of user-generated Attestation Identity Key (AIK) tied to the TPM Storage Root Key (SRK), which complicates TPM-based device usage and trustworthiness.
Innovation Solution
Generating and storing a persistent identifier and key pair using a TPM's non-volatile storage, derived from entropy values, which remains unchanged during TPM resets, allowing the persistent identifier and key pair to be used for identity verification and signing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manufacturer-provisioned Endorsement Key (EK) is used for identification, then unique hardware identification is achieved, but privacy concerns arise and the key cannot be used for signing operations
Solution Approach 1:
The patent introduces an Attestation Identity Key (AIK) as an intermediary between the EK and external systems. The AIK serves as a proxy that can be used for identification and signing operations without exposing the EK, thereby resolving the privacy concerns while maintaining the ability to perform cryptographic operations.
Solution Approach 2:
The patent extracts the identification and signing functions from the EK by creating a separate AIK. This allows the EK to remain secure and private while the AIK handles all external interactions requiring identification or digital signatures.
2Object-affected harmful factors
If Attestation Identity Key (AIK) is used as identifier, then privacy is protected and signing capability is enabled, but the identifier becomes impermanent due to TPM reset
Solution Approach 1:
The patent performs preliminary actions by creating multiple AIKs before a TPM reset occurs. These pre-created AIKs are stored securely and can be used after the reset when the original AIK is lost, ensuring continuous identification capability without requiring re-enrollment.
Solution Approach 2:
The patent changes the state of AIK persistence by storing them in a manner that survives TPM resets. This involves using the TPM's secure storage capabilities to preserve the AIK material across reset events, transforming the AIK from a transient to a persistent identifier.
3Reliability
If TPM reset operation is performed, then security is refreshed and vulnerabilities are cleared, but all derived keys including AIK are destroyed
Solution Approach 1:
The patent performs preliminary key generation by creating backup AIKs before the TPM reset operation. These pre-generated keys are stored in a secure manner that allows them to survive the reset, enabling the system to refresh security state while preserving identification capability.
4Reliability
If EK is used for decryption only, then security boundaries are maintained, but the key cannot serve as a signing key for TPM identification
Solution Approach 1:
The patent creates the AIK with multi-functionality, enabling it to serve both as an identification marker and as a signing key. This single key pair handles multiple cryptographic operations that would otherwise require different keys, increasing versatility while maintaining security boundaries through the EK-AIK relationship.
Data Source
AI summary
Systems and methods are disclosed to generate a persistent identifier for a device using a trusted platform module (TPM) of the device, so that the identifier is persistent during the lifetime of the TPM. In embodiments, during an initialization of the TPM, the system obtains an entropy value from the TPM used to generate the device's persistent identifier. The identifier is written to a non-volatile storage of the TPM so that it cannot be erased during the lifetime of the TPM. In embodiments, a persistent keys pair is generated based on the identifier, and also permanently written to the non-volatile storage. In embodiments, the persistent identifier may be measured and verified via TPM quotes. In embodiments, the persistent private key may be used to sign a nonce to prove the identity of the device.