# Applications of Information Theory II

Session Type: Lecture

Session Code: A2L-A

Location: Room 1

Date & Time: Wednesday March 22, 2023 (10:20 - 11:20)

Chair: Sanghamitra Dutta

Track: 1

Paper ID | Paper Name | Authors | Abstract |
---|---|---|---|

3031 | Physical Layer Insecurity | Muriel Médard, Ken Duffy | 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. In the finite blocklength regime, success exponents can be used to approximately evaluate the frequency with which Eve's decoding is correct in beyond-capacity channel conditions. Moreover, through GRAND, we demonstrate that Eve can constrain her decoding procedure through a query-number threshold 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, since they achieve secrecy capacity. Simulation results mimic the mathematical predictions, demonstrating the practical possibility of compromising physical layer security. |

3041 | Physical Geometry of Channel Degradation | Steve Huntsman | We outline a geometrical correspondence between capacity and effective free energy minima of discrete memoryless channels. This correspondence informs the behavior of a timescale that is important in effective statistical physics. |

3007 | Search for Extraterrestrial Intelligence as One-Shot Hypothesis Testing | Ian George, Xinan Chen, Lav Varshney | The search for extraterrestrial intelligence (SETI) struggles with a strong indeterminacy in what data to look for and when to do so. Previous information-theoretic analysis has been formulated in terms of communication. In this work, we instead formalize SETI as (quantum) one-shot asymmetric hypothesis testing. This framework holds for the detection of any technosignature including quantum signals, which are considered. Using this formalism, we unify the analysis of fundamental limits and benchmarking specific signals. We also show a practical distinction between the communication and detection scenarios and note our framework is generally computationally efficient. |