NIP-88 ====== Nostr Cash (simple Nostr cash/token/cheque) ----------------------------------- `draft` `optional` `author:benarc` Electronic cash is useful and relays should have the option to offer minting/custodial services. Other mints could exist as stand-alone clients, but relays are ideally placed to package in with their service offerings. Nostr Cash is simple and flexible. User gives a mint some money and the mint issues the user electromic cash/cheque/token that can be used as money in nostr. Nostr Cash is entirely custodial and trust based, and is just a common standard for users to send/receive value in nostr. Keepiong mints simple means more users can run, for themselves, their family, or the whole world. Relays offering mints must have a keypair and an additional nostr keypair for its mint. Nostr Cash uses derived keys, much like [NIP26](https://github.com/nostr-protocol/nips/blob/master/26.md). Each "cash" is actually just a derived private key that can be burned or passed to another user. All communication between the relay and user happen over [NIP04](https://github.com/nostr-protocol/nips/blob/master/04.md). The mints ledger is two tables `active` and `spent`: ``` active: key: , amount: , user: , timestamp: spent: key: , amount: , user: , timestamp: ``` User client cash wallet stores: ``` active: key: , amount: , relay: , relaykey: , timestamp: spent: key: , amount: , relay: , relaykey: , timestamp: ``` ## Workflows ### Mint details **For fetching info about the mint.** User DMs the relay: ```json { "mint": } ``` Relay DMs user (maybe after a check if the relays mint has restricted access): ```json { "title": , "description": , "liquiity": , "type": , "fee": , } ``` ### Minting **For creating new cash from a mint.** User DMs the relay: ```json { "amount": } ``` Relay responds with payment request, which user pays: ```json { "request": } ``` Once paid the mint generates derived keypair from the mints private key, storing in table `active`: ```json { "key": , "amount": , "user": } ``` Mint replies: ```json { "key": , "amount": } ``` User client stores: ```json { "key": , "amount": , "relay": , "relaykey": , "timestamp": } ``` ### Claiming **For cashing in cash with the mint.** User DMs relay: ```json { "key": , "amount": , "type": } ``` Relay DMs user: ```json { "type": } ``` User DMs relay: ```json { "request": , } ``` ### Sending **For sending cash to another nostr user.** User DMs relay: ```json { "key": , "amount": , "type": } ``` Mint `burns` the old record for the cash and creates a new record(s), depending on if sending user is owed change (the old record moves from `active` to `spent` table). The mint creates a new record in `active` and DMs the recipient user the private-key/cash. If change is due, another record is created in `active` and sent back to the sender user. Relay DMs user(s): ```json { "key": , "amount": } ``` User(s) client stores: ```json { "key": , "amount": , "relay": , "relaykey": , "timestamp": } ```