Stealth addresses using nostr

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@setavenger

How would you make sure that no transactions are “lost”? As nostr has no global state, several scenarios come to mind where somehow a notification is “lost” or missed.

1. Notifications don’t need to be saved forever by the relays. Once received by the wallet, it can be saved offline.

2. If multiple relays are used by the sender and recipient, they are unlikely to get lost. One of them could be run by the wallet developer.

@setavenger

It’s inherent to nostr that if Alice and Bob don’t share a relay Bob will not see notes broadcasted by Alice. So some prior agreement on which relays to use would be needed?

Some common relays would exist if they are using the same wallet. Other wallets may agree on using the same list of relays.

@setavenger

If a relay deletes a note and before Bob has seen the note he will never know of the payment either. I guess one could solve this with a confirmation message. Alice could rebroadcast the notification note until Bob confirms receiving the notification. But this would only work if relay sets have an overlap.

There is no incentive for a relay to delete the event although broadcasting the event to multiple relays would avoid this. Confirmation message could also be used in the protocol.

@setavenger

Another worry I’d have are malicious actors flooding the receiver with fake notifications. Silent Payments in it’s “base case” checks Transactions accepted by a node, which has protection (e.g. PoW for confirmed txs) against transaction flooding.

Fake notifications can be managed by normal spam filtering used in other nostr clients and relays.

@setavenger

I’m not deep in the weeds on nostr’s recent developments on private messaging without leaking metadata. It seems though that pairing your idea with silent payments could be quite interesting. i.e. I could see nostr notifications as an easy way to notify receivers of new Silent Payments. They could always fallback to a full chain scan if necessary (e.g. Bob suspects a missed transaction). My worries for nostr notifications were/are always the metadata leakage but I think some efforts were made to reduce that issue. Would be interested in hearing your opinions on the risk of metadata leakage when notifying receivers.

1. Pairing the idea with silent payments sounds interesting and I had discussed it with @moonsettler.
2. Metadata leaks are fixed and only exist in NIP 4.

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Note: Electrum wallet already uses nostr relays in the wallet. So it will be easier to implement this as a plugin.