Pre-Shared Key Synchronization for Low-Latency Secure Control
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Solution Overview
Problem
Conventional communication protocols in automotive in-vehicle networks face significant latency and security risks due to the need for key agreement messages to distribute shared keys, which is unsuitable for real-time control systems.
Innovation Solution
Implementing a system that uses locally stored key counters and pre-shared keys, eliminating the need for separate key agreement messages by including a representation of the key counter in each secured message, and incorporating live membership tracking to guard against replay attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated key agreement messages are used to distribute shared keys, then security is improved, but communication latency increases and real-time control is compromised
Solution Approach 1:
The patent combines key distribution and data communication into a single message format. The secured message simultaneously carries both the data payload and the key agreement information (counter value and integrity check), eliminating the need for separate key agreement messages and reducing communication latency while maintaining security
Solution Approach 2:
The system pre-distributes base keys through secure out-of-band channels before runtime, and uses counter values that are preliminarily synchronized among all nodes. This preliminary key establishment allows for rapid key derivation during operation without requiring time-consuming key exchange protocols
2Reliability
If key counters are included in each secured message, then key synchronization is improved, but message overhead increases
Solution Approach 1:
The patent applies different levels of security and synchronization to different parts of the system. Instead of including full keys in every message, it uses compact counter values (e.g., 32-bit integers) that require minimal overhead but provide sufficient information for key derivation and synchronization at the local node level
Solution Approach 2:
The system changes the representation of key material from full-length keys to condensed counter values that can be efficiently transmitted. The counter values serve as compact parameters that enable rapid key derivation while minimizing message overhead, and their integrity is verified through cryptographic hash functions
3Reliability
If live membership tracking is implemented, then security against replay attacks is improved, but system complexity increases
Solution Approach 1:
The patent implements a challenge-response mechanism where the controller sends challenge messages to nodes, and nodes respond with their current counter values. This feedback loop allows the controller to verify that nodes are alive and synchronized, providing security against replay attacks while using simple, well-established cryptographic protocols
Solution Approach 2:
Each node maintains its own counter value locally and uses it to derive keys and generate responses autonomously. The nodes self-manage their key material and synchronization state without requiring complex centralized key management infrastructure, reducing overall system complexity
Data Source
AI summary
The described techniques address issues to achieve key agreement without the need to exchange separate key agreement messages and, consequently, meets the stringent starting time requirements for real-time control systems. This is achieved using a group-wide key counter, with each node storing the latest value of this counter that was observed via the last received secured message. This counter value increases monotonically, and nodes maintain synchronization by transmitting this counter value (or a representation of the counter value) in each secured message. The use of key counters may be extended to guard against weak replay attacks via the implementation of a live membership tracking solution, which defines one or more membership groups. Each node within a membership group may request, or “challenge” other nodes with the same membership group at any time to verify their online status, and this online status may be maintained over time.