Multi-Access Coded Caching with Secure Delivery

The multi-access variant of the coded caching problem in the presence of external wiretappers is investigated. A multiaccess coded caching scheme with K users, K caches and N files, where each user has access to L neighbouring caches in a cyclic wrap-around manner, is proposed, which is secure against the wiretappers. Each transmission in the conventional insecure scheme will be now encrypted by a random key. The proposed scheme uses a novel technique for the key placement in the caches. It is also shown that the proposed secure multi-access coded caching scheme is within a constant multiplicative factor from the information-theoretic optimal rate for $L\displaystyle \geq\frac{K}{2}$ and $N\geq 2K$.