You are confusing offline signing with online authentication. Amber signs Nostr events locally because Nostr requires signing every event. Pubky does not. Pubky establishes revocable sessions so apps can authenticate without repeatedly touching the identity key. Ring needs network access to complete the login handshake, not to export keys or sign content. You make a key, you sign in to a homeserver, you take the key offline, you are done. No more keys needed until you want to sign in to another server or app. You only need to be online to auth or update your server location. Otherwise the key is mostly not used. Pubky allows actual cold keys that only need to be warmed if you move servers or add more apps. You can keep Ring offline 90% of the time.