Encrypted Videoconference Liveness Using Periodic Nonce Validation
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Solution Overview
Problem
Videoconferencing systems often fail to enforce liveness requirements, allowing attackers to arbitrarily delay communications, which poses a threat, especially in real-time encrypted sessions.
Innovation Solution
Participant devices generate nonces at regular intervals and transmit them to the host device, which incorporates these strings into communications to ensure liveness by matching them with the most recent nonce generated by the participant device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liveness requirements are not enforced in encrypted videoconferences, then system simplicity is maintained, but security and integrity are compromised allowing arbitrary delay attacks
Solution Approach 1:
The system generates nonces in advance at regular time intervals and stores them in a buffer before they are needed for validation. This preliminary generation and storage of nonces allows the system to quickly verify liveness without complex real-time computation, resolving the contradiction between reliability and complexity
Solution Approach 2:
Nonces serve as an intermediary mechanism between the liveness requirement and the encrypted communication protocol. Instead of directly enforcing liveness through complex protocol modifications, the system uses nonces as a simple token that mediates the verification process, maintaining protocol simplicity while ensuring security
2Reliability
If nonce validation is performed for every communication, then security against delay attacks is improved, but communication overhead increases
Solution Approach 1:
Nonces are generated at periodic time intervals (e.g., every second) rather than continuously or on-demand. This periodic generation creates a predictable pattern that simplifies validation logic and reduces computational overhead, allowing security to be maintained without excessive time loss
Solution Approach 2:
The system generates nonces at a fixed rate that may be higher than the minimum required for security. This excessive generation ensures that nonces are always available for validation without waiting for specific events, reducing validation time and overhead while maintaining strong security
3Ease of operation
If a fixed time interval is used for nonce generation, then system simplicity is maintained, but adaptability to varying network conditions is reduced
Solution Approach 1:
The system transitions from a static fixed-time interval to a dynamic adaptive interval for nonce generation. The interval automatically adjusts based on detected network conditions (latency, packet loss), allowing the system to remain simple in operation while adapting to varying network environments through automated parameter adjustment
Data Source
AI summary
A liveness requirement can be enforced on a videoconference by performing some techniques described herein. For example, a system can sequentially generate strings during a videoconference. The system can sequentially transmit the strings to a host device associated with a host of the videoconference. The system can receive a communication from the host device during the videoconference. The system can determine whether the communication includes a most recently generated string among the strings. Based on determining that the communication excludes the most recently generated string, the system can discard the communication as outdated.