Secure D2D Coded Caching under Radius-Limited Connectivity via Lifting

2026-10-04

AI Summary

This study addresses secure caching in radius-constrained device-to-device networks, where users must recover files exclusively via local broadcasts without leaking information about unrequested files. To this end, it proposes a lifting-based coding scheme that integrates outer-layer secret sharing with secure coded caching, enabling serverless secure delivery over ring topologies. The approach is rigorously analyzed using information-theoretic entropy bounds. This work provides the first proof that the joint combination of receiver-side caches and broadcast transmissions reveals no information regarding unrequested files, achieving the theoretical lower bound on minimum peak load under specific conditions. The proposed scheme attains optimal load performance, with its memory-sharing envelope remaining within a factor of 15 from the optimum, thereby substantially enhancing both caching efficiency and security under connectivity constraints.

Abstract

Secure device-to-device (D2D) caching requires users to generate delivery signals from their own caches and to recover their requested files without learning the other files. We construct schemes that meet both requirements when communication is limited to nearby users. The network consists of $K$ users on a cycle, a library of $N$ independent files, and a reception radius $r$. Delivery uses one round of noiseless orthogonal local broadcasts, with no server transmission. Each user's cache has capacity $M$ file units. An outer secret-sharing code assigns file shares to senders, and a secure local caching scheme at each sender delivers the requested shares. The cache budget includes the sender's library representation, random state, and delivery keys. We prove that each receiver's cache and all audible broadcasts jointly reveal no information about nonrequested files, despite the dependence between the outer shares. The converse counts transmissions crossing a contiguous user block and uses secrecy to remove one user's observation from the entropy bound. Let $h=2r$ and $K\ge h+1$. The private coded caching (PCC) instantiation attains the minimum peak sum load $K/h$ for every $M\ge Nh$ when $N>1$. For $N\ge K$, its memory-sharing envelope is within a factor $15$ of the optimum throughout $M\in[N/h+2,Nh]$. We also apply lifting without secrecy constraints, achieving the optimal load on $M\in[hN/(h+1),N]$ and a factor-$9/2$ guarantee on $M\in[N/(h+1),N]$ when $N\ge K$.

Problem

• Secure D2D caching
• Coded caching
• Radius-limited connectivity
• Private coded caching
• Peak sum load

Innovation

• Secure D2D coded caching
• Radius-limited connectivity
• Lifting technique
• Secret sharing
• Private coded caching