发表机构
RPTU University Kaiserslautern-Landau; Wuhan University; TU Dresden; TU Berlin; German Research Center for Artificial Intelligence (DFKI)（凯泽斯劳滕-兰道技术大学; 武汉大学; 德累斯顿工业大学; 柏林工业大学; 德国人工智能研究中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
针对流量分析防御中覆盖流量未被利用的问题，提出通过垃圾分布塑造空闲时隙波形，在块z信道模型下设计MAP接收器，以Stackelberg博弈对抗KL不可区分性观察者，显著降低检测指数并最小化吞吐量损失。
AI 中文摘要
针对流量分析的网络防御用覆盖流量填充空闲时隙，然而承载覆盖流量的物理层仍向上层提供静默空闲链路的仅擦除模型，使得覆盖内容未被利用。我们塑造该内容：空闲时隙波形从码本补集中按设计分布（即垃圾分布）抽取，该分布旨在对抗公开设计的被动观察者，同时上层保持其块z信道模型。最大后验（MAP）接收器简化为对最佳码字与先验加权垃圾聚合之间的对数似然比上的单一阈值；其错误是上层无法检测的静默损坏以及重传吸收的擦除。因此接收器设计是一维的，在静默损坏上限下最小化擦除，而联合设计是针对Kullback-Leibler（KL）不可区分性度量的Stackelberg博弈，通过交替凸松弛求解，并由独立的强化学习策略加以证实。在速率3/4的(16,12)奇偶校验（LDPC）码上，针对一个知道自身信道但发射机仅统计上知道其信道的观察者，相对于均匀覆盖，塑形垃圾将观察者的Stein检测指数降低41%至48%，在10 dB跨度和活动率上保持平坦。在合法链路变得可靠的点以下，没有覆盖分布允许工作点；在该点，塑形消耗约百分之一的吞吐量，而在其上方2 dB处无可测量损失。
英文摘要
Networking defenses against traffic analysis fill idle slots with cover traffic, yet the physical layer carrying it still hands upper layers the erasure-only model of a silent-idle link, leaving the cover content unexploited. We shape that content: the idle-slot waveform is drawn from the codebook complement under a design distribution, the \emph{litter distribution}, chosen to defeat a public-design passive observer while the upper layer keeps its block z-channel model. The maximum a posteriori (MAP) receiver reduces to a single threshold on the log-likelihood ratio between the best codeword and the prior-weighted litter aggregate; its errors are silent corruptions the upper layer cannot detect and erasures that retransmission absorbs. Receiver design is thus one-dimensional, minimizing erasure under a cap on silent corruption, and the joint design a Stackelberg game against a Kullback-Leibler (KL) indistinguishability metric, solved by an alternating convex relaxation and corroborated by an independent reinforcement-learning policy. On a rate-$3/4$ $(16,12)$ parity-check (LDPC) code against an observer who knows her own channel but whose channel the transmitter knows only statistically, shaped litter cuts the observer's Stein detection exponent by $41$ to $48\%$ relative to uniform cover, flat over a $10$~dB span and in the activity rate. Below the point where the legitimate link turns reliable, no cover distribution admits an operating point; at that point shaping costs about one percent of throughput, and nothing measurable $2$~dB above it.
CommentsSubmitted to IEEE TCOM
