Temporary Functionality Enablement for Secure Devices via Expiring HMAC Keys
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Solution Overview
Problem
Secure processing devices are vulnerable to security breaches when credentials or reusable cryptographic keys are stored, necessitating a method to unlock device functionality without storing credentials and using reusable keys.
Innovation Solution
A method involving storing public keys for trusted devices, generating a unique HMAC key, transmitting and verifying a signed HMAC, and enabling device functionality based on comparison, with the HMAC key expiring under configurable conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If credentials or reusable cryptographic keys are stored in the secure device to enable unlocking functionality, then device access control is improved, but security vulnerability increases
Solution Approach 1:
The patent extracts the credential storage function from the secure device itself. Instead of storing credentials locally, the system uses a remote credential vault where credentials are stored externally. The secure device only holds references or tokens that point to the actual credentials, thereby eliminating the security vulnerability of local credential storage while maintaining access control functionality.
Solution Approach 2:
The patent introduces an intermediary credential vault system that mediates between the user and the secure device. This intermediary stores the actual credentials securely and provides temporary access tokens to the device, allowing authentication without the device ever possessing the actual credentials. This resolves the contradiction by enabling access control through the intermediary while keeping the secure device free of credential storage vulnerabilities.
2Reliability
If credentials are stored by the device to enable unlocking, then authentication capability is improved, but security policy compliance deteriorates
Solution Approach 1:
The patent extracts credential storage from the device to an external credential vault, allowing the device to maintain authentication capability through token-based verification while complying with security policies that prohibit local credential storage. The device authenticates users by verifying tokens obtained from the vault rather than by storing credentials locally.
Solution Approach 2:
The patent implements dynamic credential access where credentials are temporarily provided to the device only when needed for authentication, rather than being permanently stored. The credential vault can dynamically issue, revoke, and manage access tokens, allowing the system to adapt to changing security policies and authentication requirements while maintaining reliable authentication capability.
3Ease of operation
If reusable cryptographic keys are used to unlock the device, then access management is improved, but security breach risk increases
Solution Approach 1:
The patent replaces reusable cryptographic keys with disposable, single-use authentication tokens. Each token is generated temporarily for a specific authentication event and becomes invalid after use or expiration. This eliminates the security risk of reusable keys while maintaining ease of access management, as the credential vault can automatically generate and manage these short-lived tokens without requiring complex key management infrastructure.
Data Source
AI summary
A method is provided for temporarily enabling functionality of a secure device. The method includes storing public keys for respective trusted devices of at least one trusted device, storing device-unique data that is unique for the secure device, generating a unique hashed-based message authentication code (HMAC) key, computing, based on the HMAC key and the device-unique data, a unique HMAC, transmitting the HMAC to a trusted device of the at least one trusted device, receiving a signed HMAC from the trusted device, wherein the signed HMAC is the HMAC as signed by the trusted device using a private key of the trusted device, decrypting the signed HMAC using the public key for the trusted device, comparing the decrypted signed HMAC to the HMAC, and enabling functionality of the secure device based on a result of the comparison.