Mostro specification for clients


All messages broadcasted by Mostro daemon are Parameterized Replaceable Events and use 38383 as event kind, a list of standard event kinds can be found here

Communication between users and Mostro

All messages from/to Mostro should be a Nostr event kind 4, the content field of the event should be a base64-encoded, aes-256-cbc encrypted JSON-serialized string (with no white space or line breaks) of the following structure:

  • version: Version of the protocol, currently 1
  • pubkey (optional): Real pubkey of the user, if present the message is signed with the real pubkey, this is used when users are sending messages from ephemeral keys
  • action: Action to be performed by Mostro daemon
  • content (optional): Content of the message, this field is optional and depends on the action

These fields are relative to the wrapper, here an example of a fiat-sent Order message, in this case id is the Order Id:

  "order": {
    "version": 1,
    "id": "ede61c96-4c13-4519-bf3a-dcf7f1e9d842",
    "pubkey": "0001be6bd50247846a28cce439a10470a39b1b6c81d5c3be2475156a413e1e3a",
    "action": "fiat-sent",
    "content": null


For all examples the participants will use this keys:

  • Mostro's pubkey dbe0b1be7aafd3cfba92d7463edbd4e33b2969f61bd554d37ac56f032e13355a
  • Seller's real pubkey 00000ba40c5795451705bb9c165b3af93c846894d3062a9cd7fcba090eb3bf78
  • Seller's ephemeral pubkey 1f5bb148a25bca31506594722e746b10acf2641a12725b12072dcbc46ade544d
  • Buyer's real pubkey 0000147e939bef2b81c27af4c1b702c90c3843f7212a34934bff1e049b7f1427
  • Buyer's ephemeral pubkey 9a42ac72d6466a6dbe5b4b07a8717ee13e55abb6bdd810ea9c321c9a32ee837b

Ephemeral keys

Mostro clients should use newly fresh keys to communicate with Mostro, indicating the pubkey where they want to be contacted by the counterpart in the pubkey field of the message, this way orders and users can't be easily linked, buyer_pubkey and seller_pubkey fields are each party real pubkeys.