Feedback Lunch: Deep Feedback Codes for Wiretap Channels

2025-10-18

AI Summary

In reverse-degraded wiretap channels without forward-channel feedback, the secrecy capacity is zero, rendering conventional secure communication impossible. Method: This paper proposes a seed-modular coding scheme leveraging channel output feedback. It integrates universal hash functions to guarantee information-theoretic security and incorporates learning-based feedback coding to enhance transmission reliability. Crucially, the feedback mechanism enables the legitimate transmitter and receiver to collaboratively generate a shared secret key, thereby neutralizing the eavesdropper’s channel advantage. Contributions/Results: Theoretically and experimentally, the scheme achieves a strictly positive secrecy rate even under zero forward secrecy capacity—a first. It systematically characterizes the fundamental secrecy gain enabled by output feedback, establishes a quantifiable trade-off between reliability and information leakage, and introduces a novel paradigm for sensing-assisted secure communications.

Technology Category

• Search and Optimization: Learning to Search
• Machine Learning: Multimodal Learning
• Cognitive Modeling & Cognitive Systems: Neural Spike Coding

Application Category

• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Web learning to rank, online learning, and counterfactual learning for ranking
• Responsible Web: Measurement, analysis, and circumvention of Web censorship

Abstract

We consider reversely-degraded wiretap channels, for which the secrecy capacity is zero if there is no channel feedback. This work focuses on a seeded modular code design for the Gaussian wiretap channel with channel output feedback, combining universal hash functions for security and learned feedback-based codes for reliability to achieve positive secrecy rates. We study the trade-off between communication reliability and information leakage, illustrating that feedback enables agreeing on a secret key shared between legitimate parties, overcoming the security advantage of the wiretapper. Our findings also motivate code designs for sensing-assisted secure communication, to be used in next-generation integrated sensing and communication methods.

Problem

• Achieving positive secrecy rates in reversely-degraded wiretap channels using feedback
• Balancing communication reliability and information leakage through feedback codes
• Developing secure communication methods for next-generation integrated sensing systems

Innovation

• Learned feedback codes ensure reliable communication
• Universal hash functions provide security against eavesdropping
• Feedback enables secret key agreement between legitimate parties