nips/03.md

NIP-03
======

OpenTimestamps Attestations for Events
--------------------------------------

`draft` `optional` `author:fiatjaf` `author:constant`

This NIP defines an event with `kind:1040` that can contain an [OpenTimestamps](https://opentimestamps.org/) proof for any other event:

```json
{
  "kind": 1040
  "tags": [
    ["e", <event-id>, <relay-url>],
    ["block", <block-height-as-string>, <block-hash>],
    ["alt", "opentimestamps attestation"]
  ],
  "content": <base64-encoded OTS file data>
}
```

- The OpenTimestamps proof MUST prove the referenced `e` event id as its digest.
- The `block` tag is optional, it exists to establish a minimum date since which the given event has existed.
- The `content` MUST be the full content of an `.ots` file containing at least one Bitcoin attestation. This file SHOULD contain a **single** Bitcoin attestation and no reference to "pending" attestations since they are useless in this context.

### Example OpenTimestamps proof verification flow

Using [`nak`](https://github.com/fiatjaf/nak), [`jq`](https://jqlang.github.io/jq/) and [`ots`](https://github.com/fiatjaf/ots):

```bash
~> nak req -i e71c6ea722987debdb60f81f9ea4f604b5ac0664120dd64fb9d23abc4ec7c323 wss://nostr-pub.wellorder.net | jq -r .content | ots verify
> using an esplora server at https://blockstream.info/api
- sequence ending on block 810391 is valid
timestamp validated at block [810391]
```