Looks like wizardforhire was talking about something like distributed encrypted backups. The simple version is, others store your stuff for you (and you store theirs), but they can't read it, because only you have the key.
Add to that a way to authorise people to decrypt your stuff (and, ideally, ways to revoke those rights), and you get the the whole thing.
Distributed backup already exists and can possibly work.
But IIReadC you wanted to cache media on peers devices to allow them to see/listen to it.
That cannot work unless you trust your friends completely (or keep your friends under constant surveillance, and hardly even then) as once they see it on their screen they can photograph or record your media, if necessary using an external device (e.g. a camera) and store it or share it.
Also, once your friends has access to it that makes your friends a target for bad actors that might want to trick or coerce your friends into sharing.
Add to that a way to authorise people to decrypt your stuff (and, ideally, ways to revoke those rights), and you get the the whole thing.