标题： 物理层不安全性 显示英文标题

标题： Physical layer insecurity

摘要： 在经典的窃听模型中，爱丽丝希望可靠地与鲍勃通信，而不会被在退化信道上窃听的夏娃听到。 实现物理层安全的系统通常依赖于一个纠错码，其速率低于爱丽丝和鲍勃信道的香农容量，因此鲍勃可以可靠地解码，但高于爱丽丝和夏娃的信道，因此夏娃无法可靠地解码。 对于有限块长度范围，已经提出了几种度量来表征信道信息泄露。 在这里，我们评估了一个新的度量——成功指数，并证明可以通过使用猜测随机加性噪声解码（GRAND）来破坏任何中等长度码的物理层安全性。 成功指数是误差指数的自然超越容量类比，误差指数表征当码率超过香农容量时最大似然解码正确的概率，该概率随着码长呈指数衰减。 成功指数可用于近似评估夏娃在超越容量信道条件下解码正确的频率。 通过使用GRAND，我们证明夏娃可以限制她的解码过程，使得当她确定一个解码时，它有很高的可能性是正确的，从而真实地揭示一部分爱丽丝和鲍勃的通信，显著破坏他们的通信。 我们提供了确定成功指数以及使用二进制对称信道作为示例来评估夏娃查询数阈值的一般数学表达式。 由于GRAND算法与码书无关，并可以解码任何码结构，我们提供了随机线性码的实证结果作为示例。 仿真结果展示了破坏物理层安全的实际可能性。 显示英文摘要

摘要： In the classic wiretap model, Alice wishes to reliably communicate to Bob without being overheard by Eve who is eavesdropping over a degraded channel. Systems for achieving that physical layer security often rely on an error correction code whose rate is below the Shannon capacity of Alice and Bob's channel, so Bob can reliably decode, but above Alice and Eve's, so Eve cannot reliably decode. For the finite block length regime, several metrics have been proposed to characterise information leakage. Here we assess a new metric, the success exponent, and demonstrate it can be operationalized through the use of Guessing Random Additive Noise Decoding (GRAND) to compromise the physical-layer security of any moderate length code. Success exponents are the natural beyond-capacity analogue of error exponents that characterise the probability that a maximum likelihood decoding is correct when the code-rate is above Shannon capacity, which is exponentially decaying in the code-length. Success exponents can be used to approximately evaluate the frequency with which Eve's decoding is correct in beyond-capacity channel conditions. Through the use of GRAND, we demonstrate that Eve can constrain her decoding procedure so that when she does identify a decoding, it is correct with high likelihood, significantly compromising Alice and Bob's communication by truthfully revealing a proportion of it. We provide general mathematical expressions for the determination of success exponents as well as for the evaluation of Eve's query number threshold, using the binary symmetric channel as a worked example. As GRAND algorithms are code-book agnostic and can decode any code structure, we provide empirical results for Random Linear Codes as exemplars. Simulation results demonstrate the practical possibility of compromising physical layer security.