nips/63.md

NIP-63
======

Signed Filters
--------------

`draft` `optional`

Event kind `33012` is used to represent one or more Nostr filters. 

The `d` tag represents the subscription id and the `filter` tag contains the JSON-stringified [NIP-01](01.md) filter. 

The optional `relays` tag contains the destination relays the filter was designed to download events from.

The optional `authorized` pubkey contains the pubkey authorized to re-use this filter and receive events on behalf of the user. 

```js
{
  "kind": 33012,
  "tags": [
    ["d", "<subscription_id>"],
    ["filter", "<filter1>"],
    ["filter", "<filter2>"],
    ["authorized", "<32-bytes lowercase hex of a pubkey>"], 
    ["relays", "<relay1>", "<relay2>", ...],
    ["expiration", "<unix timestamp>"],
  ],
  "content": "",
  // ...other fields
}
```

They are submitted to supporting relays via `SREQ` command, with the following format: 

```js
["SREQ", <kind-33012>, <kind-33012>, ...]
```

Supporting relays interpret the `filter` tags in the same way they do with `REQ` while automatically authenticating the signer. 

Supporting relays MUST authenticate the `authorized` key if present. 

Relays MAY reject these filters based on `created_at`. 

An expiration tag MAY be used to limit the reuse of the filter. 

## Motivation

Push Notification servers can use these events to query private relays on behalf of users and push events down to mobile phones. 

The goal is to be able to support `AUTH` from multiple users in the same connection. As a side effect, this approach removes the user `AUTH` round trip (but not the delegation `AUTH`). 

Trusted proxies can use these event types to query relays on behalf of the user.