High-Availability Secure Communication Startup with Stored Session Keys
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Solution Overview
Problem
Establishing secure communication between devices in a distributed control system, such as an aircraft system, can be time-consuming due to methods like Diffie-Hellman key exchange requiring multiple transmissions and several seconds to complete, which is undesirable for quick system startups or resets.
Innovation Solution
Devices use a previously negotiated session key for immediate encrypted communication if available, transitioning to unencrypted communication if no session key exists, and negotiate a new session key during ongoing communication, storing it for future use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Diffie-Hellman key exchange is used to establish secure communication, then security is improved, but communication establishment time increases to several seconds
Solution Approach 1:
The system performs preliminary actions by pre-establishing and storing session keys in non-volatile memory before actual communication is needed. When communication is required, the system checks for existing session keys and uses them immediately, avoiding the time-consuming Diffie-Hellman key exchange process. This preliminary preparation of security credentials resolves the contradiction by enabling fast communication establishment while maintaining security through pre-negotiated keys.
Solution Approach 2:
The system dynamically adapts its behavior based on the presence or absence of pre-negotiated session keys. When a session key exists, it uses encrypted communication with that key for immediate connection. When no session key is available, it falls back to unencrypted communication and performs Diffie-Hellman key exchange in the background. This dynamic adaptation allows the system to optimize between speed and security based on real-time conditions, resolving the time-security contradiction.
2Reliability
If session key negotiation is performed before communication starts, then secure transmission is ensured, but system startup time increases
Solution Approach 1:
The system performs the preliminary action of pre-negotiating and storing session keys during system initialization or previous operations, so that when new communication is needed, the keys are already available in non-volatile memory. This eliminates the need to perform time-consuming key exchange protocols during system startup or communication initiation, thereby maintaining both security and startup speed.
Solution Approach 2:
The system maintains continuous availability of session keys by storing them in non-volatile memory and checking for their presence before each communication session. This continuity ensures that secure communication can start immediately without interruption or delay for key negotiation, resolving the contradiction between ensuring secure transmission and maintaining fast startup.
3Speed
If unencrypted communication is used for quick connection, then communication speed is improved, but security is compromised
Solution Approach 1:
The system performs preliminary verification of pre-negotiated session keys before enabling encrypted communication. By checking whether valid session keys exist in non-volatile memory, the system can confidently use encrypted communication from the start without needing to perform time-consuming key exchange, thus achieving both speed and security simultaneously rather than sacrificing one for the other.
Solution Approach 2:
The system uses feedback from checking the presence of session keys to determine the appropriate communication mode. When session keys are available, it feedbacks with encrypted communication for both speed and security. When keys are unavailable, it feedbacks with unencrypted communication and performs key exchange in the background. This feedback mechanism allows the system to optimize performance while maintaining security based on real-time conditions.
Data Source
AI summary
A distributed control system includes an electronic control unit to establish secure communication with a distributed control module. Upon determination that a previously negotiated session key is stored on the electronic control unit, the electronic control unit transmits encrypted communications with the distributed control module using the previously negotiated session key, negotiates a new session key with the distributed control module, and stores the new session key. Upon determination that the previously negotiated session key is not stored on the electronic control unit, the electronic control unit negotiates the new session key with the distributed control module. After negotiating the new session key with the distributed control module, the electronic control unit ceases transmission of unencrypted communications with the distributed control module, transmits encrypted communications with the distributed control module using the new session key, and stores the new session key.