Temporal Certificate Chains for Offline IoT Authentication
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Solution Overview
Problem
IoT devices often remain offline for extended periods, making it challenging to update Root certificates, which increases the risk of certificate compromise due to prolonged usage of outdated certificates.
Innovation Solution
Implementing temporal certificate chains where each certificate is signed using the private key of the previous certificate, allowing for sequential authentication and updating of Root certificates, even when devices are offline, by sending limited chains and using the most recent certificate for authentication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Root certificates are updated frequently using traditional cross-signing process, then security risk is reduced, but the process can only be performed if devices are connected to server before original certificate expires
Solution Approach 1:
The patent applies preliminary action by pre-provisioning multiple Root certificates (including future certificates) into devices during manufacturing or initial setup. This allows devices to have updated certificates ready before they are actually needed, eliminating the dependency on timely server connections for certificate updates. The device can switch to pre-provisioned certificates at appropriate times without requiring online presence during the update process.
Solution Approach 2:
The patent segments the certificate update process by dividing it into separate phases: (1) pre-provisioning of multiple Root certificates during manufacturing/initial setup, (2) selective activation of certificates based on time or events, and (3) independent update of individual certificates without requiring device online presence. This segmentation allows certificate management to proceed independently of device connectivity status.
2Ease of operation
If devices remain offline for extended periods, then device autonomy is maintained, but Root certificate updating becomes challenging and security risk increases
Solution Approach 1:
Multiple Root certificates are pre-provisioned into devices during manufacturing or initial setup, creating a local certificate repository. This preliminary action ensures that devices have updated certificates available locally without needing to connect to servers during operation. The device can autonomously select and use the appropriate certificate based on time or other criteria, maintaining both autonomy and security.
3Ease of operation
If single Root certificate is used for extended periods, then device autonomy is maintained, but security risk of certificate compromise increases
Solution Approach 1:
The patent segments the certificate system by implementing multiple Root certificates with different validity periods and purposes. Instead of relying on a single long-lived certificate, the system divides certificate functionality across multiple shorter-lived certificates. This segmentation limits the impact of potential compromise to individual certificates rather than the entire system, reducing overall security risk while maintaining device autonomy through local certificate selection.
Solution Approach 2:
The patent employs the principle of short-lived certificates by provisioning multiple Root certificates with limited validity periods. Each certificate is designed to be used for a specific timeframe or purpose, after which it expires or becomes obsolete. This approach reduces security risk because even if a certificate is compromised, the window of vulnerability is limited. The device autonomously manages these short-lived certificates without requiring continuous server connections.
Data Source
AI summary
Chains of cryptographic certificates are used for server authentication in a recursive manner. A device requires a Root certificate to authenticate a server, where the Root certificate is changed periodically. Each Root certificate is signed using a prior Root certificate. When a device is required to perform an authentication, multiple Root certificates forming a chain are provided to the device. The device authenticates the first Root certificate in the chain using a previously stored Root certificate, and authenticates each other Root certificate in the chain using a prior Root certificate in the chain. Upon authenticating the last Root certificate in the chain, the authentication can be completed. An associated server is also provided. The device can store the last Root certificate in the chain for use in defining subsequent chains.