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 `relay` tag lists the authorized relays the filter can download events from.

The optional `authorized` tag lists the pubkeys that are authorized to receive authed 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>"], 
    ["relay", "<relay1>"],
    ["relay", "<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. 

Relays MUST authenticate the `authorized` key if present. 

Relays MUST verify if they are included in the `relay` tag list if present. 

Relays MUST comply with the `expiration` 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.