No, but it's a very similar design with relays. Nostr has largely failed to provide a private and secure DM protocol so far so that should be a good thing. nostr:nevent1qqs04jkx6rxfnzs8a3dc3gxsqpvjhe9yat74y3hdmfw53efeu22g6qcqrau8x 

 Actually, in a way it is, it's not THE Nostr protocol but it is notes (messages) and (not really other stuff) transmitted by relays. 

 Media and files could count as other stuff which is transmitted via relays rather than being uploaded to a single webserver like what happens on Nostr. Here's an article if you want to learn more about SimpleX's file transfer protocol specially https://simplex.chat/blog/20230301-simplex-file-transfer-protocol.html