Encrypted Probe Echoing for Positive Secrecy Transmission
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Solution Overview
Problem
Existing secret-message transmission systems are constrained by one-way communication models, leading to zero secrecy rates when eavesdropper channels are stronger than legitimate channels, and lack integration of wireless and wireline, analog and digital channels, requiring multiple iterative transmissions.
Innovation Solution
The system and method for secret-message transmission (STEEP) involves two phases: Alice sends probing signals to Bob and Eve, and Bob echoes encrypted probes back, creating a stronger effective channel from Bob to Alice than to Eve, allowing a positive secrecy rate even if Eve's channel is stronger, applicable to wireless or wireline, analog or digital channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one-way transmission model is used, then system complexity is reduced, but secrecy rate becomes zero when eavesdropper channel is stronger than legitimate channel
Solution Approach 1:
The patent inverts the traditional one-way transmission model by implementing a two-way communication system where Alice sends probes to Bob and Bob echoes encrypted probes back to Alice. This inversion allows the legitimate channel to be strengthened through reciprocal communication while the eavesdropper's channel remains one-way, ensuring positive secrecy rate even when eavesdropper's initial channel is stronger.
Solution Approach 2:
The patent introduces encrypted probe echoes as an intermediary mechanism. Bob receives probes from Alice, encrypts them with his secret key, and echoes them back. This intermediary process creates an effective stronger channel from Bob to Alice that is inaccessible to Eve, resolving the contradiction between simple model and reliable secrecy.
2Reliability
If multiple iterative transmissions are used, then secrecy rate is improved, but communication time and complexity increase
Solution Approach 1:
The patent implements continuous useful action by having Bob immediately echo the encrypted probes back in the same coherence period without waiting for multiple iterative transmissions. This continuous two-way communication achieves secrecy rate improvement in a single round-trip, eliminating time loss associated with multiple iterations while maintaining high secrecy through the encrypted echo mechanism.
3Reliability
If channel probing is performed, then secrecy rate increases with probing symbols, but system complexity and overhead increase
Solution Approach 1:
The patent makes the probe signals serve multiple functions: they act as both channel probing signals for estimating channel conditions and as encryption keys for securing the communication. This multi-functionality increases secrecy rate with probing symbols while avoiding additional system complexity, as the same signals fulfill both probing and security purposes.
Solution Approach 2:
The patent merges the channel probing process with the secret key generation process. Instead of separate probing and key establishment phases, the probe signals themselves are used to generate the secret keys through the echo mechanism. This merging reduces system complexity while maintaining the benefit of increasing secrecy rate with more probing symbols.
4Measurement precision
If public pilots are used in static environments, then channel estimation is improved, but secrecy rate may decrease due to information leakage
Solution Approach 1:
The patent introduces asymmetry in how channel information is utilized. While public pilots provide symmetric channel estimation for both legitimate users and eavesdropper, the encrypted echo mechanism creates asymmetric security: Alice and Bob can exploit their mutual knowledge of the probe sequences and echo encryption, while Eve cannot, even with perfect channel estimation. This asymmetry preserves secrecy rate despite public pilot usage.
Data Source
AI summary
Provided is a system and method for secret-message transmission by echoing encrypted probes (STEEP). Specifically, STEEP may comprise, in one embodiment, two phases. For Phase 1: Alice transmits probing signals (or probes) to Bob, and most likely and unintentionally to Eve, over one or more probing channels, from which Eve must obtain a noisy version of the probes while Bob may receive a noisier version of the probes. For Phase 2: Bob echoes back his estimates of the probes, but encrypted by his secret, over one or more return channels that have much higher quality than the probing channels in phase 1.