Secure Time-Aware Authentication for Embedded Sensing and Acting Devices
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Solution Overview
Problem
Existing systems lack sufficient security regarding timing and time synchronization, providing an avenue for attacks that can compromise the validity of security certificates and manipulate sensor measurements or actuator commands.
Innovation Solution
A secure sub-system with a real-time clock (RTC) is provisioned with credentials and timestamps by a user CA within a cryptographic session, establishing a secure time-base that prevents tampering and ensures accurate timing for sensor data and actuator commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a secure sub-system with RTC is provisioned with credentials and timestamps by a user CA within a cryptographic session, then timing-based security is improved and attacks are prevented, but device complexity increases
Solution Approach 1:
The system is divided into a secure sub-system containing the RTC and cryptographic functions, separated from the main device. This segmentation isolates the critical timing security functions in a dedicated secure enclave, improving reliability while containing the complexity within a modular component that can be provisioned independently.
Solution Approach 2:
A user CA (Certificate Authority) acts as an intermediary to provision the secure sub-system with credentials and timestamps through a cryptographic session. This intermediary approach allows external security management, enabling the device to benefit from centralized security policies without permanently hosting the entire security infrastructure, thus balancing security with complexity management.
2Reliability
If timestamps and credentials are provisioned through a cryptographic session with user CA, then security against manipulation is improved, but provisioning complexity increases
Solution Approach 1:
The secure sub-system is provisioned with credentials, timestamps, and cryptographic keys during an initial setup phase before the device enters normal operation. This preliminary action ensures that all security parameters are established in advance under controlled cryptographic sessions with the user CA, preventing manipulation during runtime while keeping the ongoing operation simple.
Solution Approach 2:
The secure sub-system performs self-verification of timestamps and credentials using its provisioned cryptographic keys and the user CA's public key. This self-service capability allows the device to autonomously validate security parameters without requiring continuous external intervention, reducing provisioning complexity after the initial setup.
3Reliability
If secure timestamp attachment and signature generation are performed for sensor data, then data integrity is improved, but processing time increases
Solution Approach 1:
The timestamp attachment and signature generation operations are merged into a single atomic cryptographic operation performed by the secure sub-system. By combining these functions in the secure enclave, the system achieves data integrity protection without requiring separate processing steps, minimizing the time penalty while ensuring both timestamp and signature are generated from the same secure context.
4Reliability
If actuator commands are validated with signature and time validity range checking, then command security is improved, but operation speed decreases
Solution Approach 1:
Time validity ranges and signature verification parameters are pre-computed and stored in the secure sub-system during the provisioning phase. When actuator commands arrive, the system only needs to perform a simple timestamp comparison against the pre-stored validity range and a cryptographic signature verification, rather than performing complex validation calculations in real-time, thus maintaining security while improving execution speed.
Data Source
AI summary
Various implementations relate to controller in a system, including: a device connected to a network; and a secure sub-system connected to the device via a first wired connection, the secure sub-system configured to: establish a trusted channel with a user certificate authority (CA) via a provisioning device; receive application parameters from user CA; provision a timestamp or secure time server information based upon the timestamp or secure time server information received from the user CA; create a device identity for the device; and terminate the trusted channel after provisioning the timestamp or secure time server information and creating the device identity for the device.