Adaptive coding improves secrecy for two-way communication channels
Adaptive Coding for Two-Way Wiretap Channels with One-Sided Strong Secrecy
Information Theory
Summary
This paper looks at two-way communication systems where only one user’s message needs to stay secret from eavesdroppers. The authors develop new coding methods that adapt based on feedback, which helps keep the secret message safe even if earlier secret keys are partially revealed or misused. They prove mathematical results showing how much better adaptive methods can be compared to fixed ones. For an example type of communication channel, they also find the exact limits of how much secret information can be sent securely without adaptation.
What this means in practice
- •For network security engineers: Design secure communication protocols that adaptively protect confidentiality when only one side needs secrecy over noisy two-way channels.
- •For wireless system architects: Develop coding schemes that improve secret message transmission rates by exploiting feedback and adaptive key usage in two-way wireless links.
A theory result. No direct application yet.
Authors
Masahito Hayashi, Yanling Chen
Abstract
We study a discrete memoryless two-way wiretap channel under strong one-sided secrecy, where User 1's message is confidential and User 2's message is not required to be secret. We develop non-adaptive and key-assisted adaptive inner bounds from a common resolvability estimate for selected index components. For the adaptive construction, we prove a multiround leakage theorem that accounts both for information revealed about a key before its later use and for the possibility that an encoder uses an incorrectly decoded key. The proof includes an ideal-to-implemented coupling, deterministic codebook selection, and a growing-round argument that removes the initialization-rate loss. We eliminate the internal component rates exactly and characterize the adaptive gain at each fixed auxiliary distribution. For an open two-parameter family of binary channels, we also prove a converse for arbitrary non-adaptive stochastic codes and obtain an operational adaptive-versus-non-adaptive separation. For one representative channel, the complete non-adaptive strong one-sided secrecy capacity region is identified exactly.