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14/WAKU2-MESSAGE

Waku v2 Message

draft

Oskar Thorén <oskar@status.im>

Sanaz Taheri <sanaz@status.im>

This specification provides a way to encapsulate messages sent over Waku with specific information security goals.

Motivation

When sending messages over Waku there are multiple concerns:

We may have a separate encryption layer as part of our application
We may want to provide efficient routing for resource restricted devices
We may want to provide compatibility with Waku v1 envelopes
We may want payloads to be encrypted by default
We may want to provide unlinkability for metadata protection

This specification attempts to provide for these various requirements.

WakuMessage

A WakuMessage is what is being passed around by the other protocols, such as WakuRelay, WakuStore, and WakuFilter.

The payload field SHOULD contain whatever payload is being sent. See section below on payload encryption.

The contentTopic field SHOULD be filled out to allow for content-based filtering. See 12/WAKU2-FILTER and 13/WAKU2-STORE for more details. To enable a bidirectional bridge with Waku v1 see 15/WAKU2-BRIDGE for further requirements on this field.

The version field MAY be filled out to allow for various types of payload encryption. Omitting it means the version is 0.

The timestamp field MAY be filled out to signify the time at which the message is generated by its sender. This field holds the Unix epoch time. Omitting it means the timestamp is unspecified.

Payloads

Payloads are implemented using protocol buffers v3.

syntax = "proto3";

message WakuMessage {
  bytes payload = 1;
  string contentTopic = 2;
  uint32 version = 3;
  double timestamp = 4;
}

Payload encryption

Payload encryption depends on the version field.

Version 0

This indicates that the payload SHOULD be either unencrypted or that encryption is done at a separate layer outside of Waku.

Version 1

This indicates that payloads MUST be encrypted using 7/WAKU-DATA envelope data format spec.

This provides for asymmetric and symmetric encryption. Key agreement is out of band. It also provides an encrypted signature and padding for some form of unlinkability.

Differences from Whisper / Waku v1 envelopes

In Whisper and Waku v1, an envelope contains the following fields: expiry, ttl, topic, data, nonce.

Since Waku v2 is using libp2p PubSub, some of these fields can be dropped. The previous topic field corresponds to contentTopic. The previous data field corresponds to the payload field.

Security Consideration

In Waku, the confidentiality, integrity, and authenticity of the data must be addressed at the WakuMessage level. That is, the payload shall be encrypted or signed properly to meet the application-specific privacy needs.

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