NIPs nostr improvement proposals

NIP-01 - Basic protocol flow description

Table of Contents

Basic protocol flow description

draft mandatory

This NIP defines the basic protocol that should be implemented by everybody. New NIPs may add new optional (or mandatory) fields and messages and features to the structures and flows described here.

Events and signatures

Each user has a keypair. Signatures, public key, and encodings are done according to the Schnorr signatures standard for the curve secp256k1.

The only object type that exists is the event, which has the following format on the wire:

{

  "id": <32-bytes lowercase hex-encoded sha256 of the serialized event data>,

  "pubkey": <32-bytes lowercase hex-encoded public key of the event creator>,

  "created_at": <unix timestamp in seconds>,

  "kind": <integer between 0 and 65535>,

  "tags": [

    [<arbitrary string>...],

    // ...

  ],

  "content": <arbitrary string>,

  "sig": <64-bytes lowercase hex of the signature of the sha256 hash of the serialized event data, which is the same as the "id" field>

}

To obtain the event.id, we sha256 the serialized event. The serialization is done over the UTF-8 JSON-serialized string (which is described below) of the following structure:

[

  0,

  <pubkey, as a lowercase hex string>,

  <created_at, as a number>,

  <kind, as a number>,

  <tags, as an array of arrays of non-null strings>,

  <content, as a string>

]

To prevent implementation differences from creating a different event ID for the same event, the following rules MUST be followed while serializing:

Tags

Each tag is an array of one or more strings, with some conventions around them. Take a look at the example below:

{

  "tags": [

    ["e", "5c83da77af1dec6d7289834998ad7aafbd9e2191396d75ec3cc27f5a77226f36", "wss://nostr.example.com"],

    ["p", "f7234bd4c1394dda46d09f35bd384dd30cc552ad5541990f98844fb06676e9ca"],

    ["a", "30023:f7234bd4c1394dda46d09f35bd384dd30cc552ad5541990f98844fb06676e9ca:abcd", "wss://nostr.example.com"],

    ["alt", "reply"],

    // ...

  ],

  // ...

}

The first element of the tag array is referred to as the tag name or key and the second as the tag value. So we can safely say that the event above has an e tag set to "5c83da77af1dec6d7289834998ad7aafbd9e2191396d75ec3cc27f5a77226f36", an alt tag set to "reply" and so on. All elements after the second do not have a conventional name.

This NIP defines 3 standard tags that can be used across all event kinds with the same meaning. They are as follows:

As a convention, all single-letter (only english alphabet letters: a-z, A-Z) key tags are expected to be indexed by relays, such that it is possible, for example, to query or subscribe to events that reference the event "5c83da77af1dec6d7289834998ad7aafbd9e2191396d75ec3cc27f5a77226f36" by using the {"#e": ["5c83da77af1dec6d7289834998ad7aafbd9e2191396d75ec3cc27f5a77226f36"]} filter.

Kinds

Kinds specify how clients should interpret the meaning of each event and the other fields of each event (e.g. an "r" tag may have a meaning in an event of kind 1 and an entirely different meaning in an event of kind 10002). Each NIP may define the meaning of a set of kinds that weren't defined elsewhere. This NIP defines two basic kinds:

And also a convention for kind ranges that allow for easier experimentation and flexibility of relay implementation:

In case of replaceable events with the same timestamp, the event with the lowest id (first in lexical order) should be retained, and the other discarded.

When answering to REQ messages for replaceable events such as {"kinds":[0],"authors":[<hex-key>]}, even if the relay has more than one version stored, it SHOULD return just the latest one.

These are just conventions and relay implementations may differ.

Communication between clients and relays

Relays expose a websocket endpoint to which clients can connect. Clients SHOULD open a single websocket connection to each relay and use it for all their subscriptions. Relays MAY limit number of connections from specific IP/client/etc.

From client to relay: sending events and creating subscriptions

Clients can send 3 types of messages, which must be JSON arrays, according to the following patterns:

<subscription_id> is an arbitrary, non-empty string of max length 64 chars. It represents a subscription per connection. Relays MUST manage <subscription_id>s independently for each WebSocket connection. <subscription_id>s are not guaranteed to be globally unique.

<filtersX> is a JSON object that determines what events will be sent in that subscription, it can have the following attributes:

{

  "ids": <a list of event ids>,

  "authors": <a list of lowercase pubkeys, the pubkey of an event must be one of these>,

  "kinds": <a list of a kind numbers>,

  "#<single-letter (a-zA-Z)>": <a list of tag values, for #e — a list of event ids, for #p — a list of pubkeys, etc.>,

  "since": <an integer unix timestamp in seconds, events must be newer than this to pass>,

  "until": <an integer unix timestamp in seconds, events must be older than this to pass>,

  "limit": <maximum number of events relays SHOULD return in the initial query>

}

Upon receiving a REQ message, the relay SHOULD query its internal database and return events that match the filter, then store that filter and send again all future events it receives to that same websocket until the websocket is closed. The CLOSE event is received with the same <subscription_id> or a new REQ is sent using the same <subscription_id>, in which case relay MUST overwrite the previous subscription.

Filter attributes containing lists (ids, authors, kinds and tag filters like #e) are JSON arrays with one or more values. At least one of the arrays' values must match the relevant field in an event for the condition to be considered a match. For scalar event attributes such as authors and kind, the attribute from the event must be contained in the filter list. In the case of tag attributes such as #e, for which an event may have multiple values, the event and filter condition values must have at least one item in common.

The ids, authors, #e and #p filter lists MUST contain exact 64-character lowercase hex values.

The since and until properties can be used to specify the time range of events returned in the subscription. If a filter includes the since property, events with created_at greater than or equal to since are considered to match the filter. The until property is similar except that created_at must be less than or equal to until. In short, an event matches a filter if since <= created_at <= until holds.

All conditions of a filter that are specified must match for an event for it to pass the filter, i.e., multiple conditions are interpreted as && conditions.

A REQ message may contain multiple filters. In this case, events that match any of the filters are to be returned, i.e., multiple filters are to be interpreted as || conditions.

The limit property of a filter is only valid for the initial query and MUST be ignored afterwards. When limit: n is present it is assumed that the events returned in the initial query will be the last n events ordered by the created_at. It is safe to return less events than limit specifies, but it is expected that relays do not return (much) more events than requested so clients don't get unnecessarily overwhelmed by data.

From relay to client: sending events and notices

Relays can send 5 types of messages, which must also be JSON arrays, according to the following patterns:

This NIP defines no rules for how NOTICE messages should be sent or treated.