This is not possible with IPFS. IPFS is a fully public network. The IPFS DHT is public, so it’s not possible. Of course you can host your own backend or reverse proxy to create your own access point, but the data is still public on IPFS. Yeah unfortunately in your case, decentralized storage also means decentralized access, there’s no way to gate keep content. A happy medium could be to use a Filebase Sia bucket. That gives you access to pre-signed URLs and other S3 features, and all of the data is stored on the decentralized Sia network. However all data is encrypted server side too, preventing access by others.