TETRA MCPTT Interworking Encryption Synchronization
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Solution Overview
Problem
Existing mobile communications systems face challenges in maintaining end-to-end encryption compatibility when interworking between different systems like TETRA and LTE, as it requires decoding and re-encoding encrypted communications, which necessitates system infrastructure access to encryption keys, compromising security and quality.
Innovation Solution
A method where a communications station generates encrypted speech frames and synchronization frames according to the TETRA protocol, associates each synchronization frame with corresponding speech frames, and transmits them to the infrastructure, allowing the system to replace speech frames with synchronization frames, maintaining end-to-end encryption without revealing encryption keys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If frame stealing technique is used to transmit encryption synchronisation information in TETRA system, then sufficient air interface bandwidth is provided, but speech quality is degraded
Solution Approach 1:
The patent segments the transmission by creating separate channels for synchronisation frames and speech frames. The synchronisation information is transmitted in dedicated synchronisation frames rather than stealing speech frames, thereby maintaining speech quality while providing sufficient bandwidth for encryption synchronisation.
Solution Approach 2:
The patent introduces an intermediary mechanism where synchronisation frames are transmitted separately from speech frames. This intermediary approach allows the system to provide encryption synchronisation information without directly interfering with speech transmission, thus avoiding quality degradation.
2Adaptability or versatility
If translation function is provided to transcode encrypted communications between TETRA and LTE systems, then interworking is facilitated, but encryption key security is compromised
Solution Approach 1:
The patent extracts the encryption key from the translation function, allowing the infrastructure to transcode speech frames without accessing the encryption key. The synchronisation frames are transmitted in clear text while the speech frames remain encrypted, enabling interworking while maintaining key security.
Solution Approach 2:
The patent uses synchronisation frames as a copy of the encryption state information that can be transmitted separately. This copy allows the receiving end to synchronize decryption without requiring the infrastructure to have access to the actual encryption key, thus maintaining security while enabling translation.
3Reliability
If synchronisation frames are transmitted together with encrypted speech frames, then end-to-end encryption is maintained, but bandwidth requirements increase
Solution Approach 1:
The patent merges the synchronisation frame transmission with the existing speech frame transmission structure. By using efficient framing and coding, the synchronisation information is transmitted alongside speech frames without requiring separate dedicated bandwidth, thus maintaining encryption while optimizing bandwidth usage.
Data Source
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AI summary
A method for performing end-to-end encryption in a communications system comprising two or more inter working communications systems. A communications station of the communications system generates encrypted speech frames and one or more encryption synchronisation frames for transmission, associates each of the one or more encryption synchronisation frames with one or more corresponding encrypted speech frames of the encrypted speech frames,and transmits a set of frames comprising the encrypted speech frames and the one or more associated encryption synchronisation frames. System infrastructure of the communications system receives the set of frames, replaces one or more of the encrypted speech frames with a corresponding encryption synchronisation frame to produce a modified set of frames,and transmits the modified set of frames to one or more TETRA communications stations.