specs/standards/application/OpChan.md

---
title: OP-CHAN
name: OpChan Decentralized Forum
status: raw
category: Standards Track
tags: waku
editor: 
contributors:
  - Jimmy Debe <jimmy@status.im>
---

## Abstract

This document specifies the architecture of OpChan.
OpChan is a decentralized forum application built on the Waku protocol.

## Background

In a decentralized forum, content is hosted on multiple nodes,
making it difficult for a user's post to be censored.
Users own their post data, so data cannot be removed by a third party,
and forum boards will not rely on moderators remaining active.

OpChan is a web application hosted by some party through a web server.
The content being published by users is not stored by the server,
but by distributing the messages peer to peer.
OpChan supports ephemeral anonymous web sessions,
supporting a locally generated ED25519 key pair for identity and
signing.
Wallet-backed identities, identity key delegation, and
content stored locally while distributing messages using the [10/WAKU2](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/10/waku2.md) protocol.

- WAKU-LIGHTPUSH

## Terminology

- Cell: A discussion board or channel that hosts posts and moderation controls.
- Post: User content created within a forum.
- Comment: A reply to a `Post` or other `Comment` (threaded discussion).
- Participant: Any user able to publish or consume messages (anonymous or
  wallet-backed).
- Anonymous session: A client-generated ed25519 keypair used as
  identity for a user without a wallet identity.

## Specification

The keywords “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”,
“SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and
“OPTIONAL” in this document are to be interpreted as described in [2119](https://www.ietf.org/rfc/rfc2119.txt).

OpChan uses the [10/WAKU2](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/10/waku2.md)
network for the distribution of forum content amongst peers. 
The messages, which are [14/WAKU-MESSAGE](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/14/message.md) objects,
are cryptographically signed using ED25519 keys generated by the client locally.
Users SHOULD use the [19WAKU2-LIGHTPUSH]() protocol to send messages to Waku nodes storing the forum's content.

OpChan supports two types of messages,
content and control messages.
Content messages are user-generated content on the forum.
The message types include the following:
  
- Channel: Metadata information like name, description, and admins of a forum feed.
- Post: User content created within a cell.
- Comment: Users reply to a post or another comment.
- Vote: To cast upvote or downvote for a post or comment.
- User: Includes username, delegation proofs, and identities.
See the [Identity](#identity) section for more information.
- Bookmark: A user bookmarking a post or comment.

Control messages consist of the user activity/interactions on the forum.
This includes the management of the current forum state,
permissions, and moderations.
The message types include the following:

-    Create Channel: The initial event of creating a new channel within the forum.
-    Delegation Events: Channel admins granting or revoking channel rights.
-    Moderation Events: Channel admins are able to hide, remove, and
  pin/unpin a post or comment.
  Also, it can promote new admins and change the ownership of a channel.

### Message Format

Message routing and
discovery are handled by [23/WAKU2-TOPICS](https://github.com/vacp2p/rfc-index/blob/main/waku/informational/23/topics.md).
Each content is assigned a `pubsub_topic` that clients MUST subscribe to discovery messages from the channel.

All messages transmitted over the Waku network MUST include the following envelope fields:

``` js
{
  "id": "string", 
  "type": "CELL_CREATED | POST_CREATED | COMMENT_CREATED | VOTE | BOOKMARK | MODERATION | DELEGATION",
  "timestamp": "uint64"
  "author": "string" // author public key or wallet address
  "signature": "bytes" // ed25519 signature of the canonical serialized body
  "delegationProof": "bytes" // optional wallet signature authorizing the browser key
  "body": object // The message content
}

```

Every message SHOULD be signed using ED25519 keys from the publishing user.
Clients SHOULD verify the signature against the `author` public key and,
when present, verify `delegationProof`.

Signing Flow:

1. Serialize `body` fields in stable key order.
2. Construct signing bytes with: `type`, `timestamp`, `author` and `body`.
3. Sign with the user's cryptographic keys for the session.

- channel admin

### Identity

There are two types of identities for users,
anonymous session and wallet delegation.
A wallet delegation MAY be an ENS(Ethereum Name Service) verified user.
An anonymous session generates an Ed25519 keypair locally with the client.
The key is used to sign all messages and
a username MAY choose a username attached to the post or comments.
An anonymous user SHOULD NOT be granted an admin role, 
create moderation events, or create a channel.

A wallet delegation uses the user's wallet private key to sign a delegation message,
the `delegationProof`.
The `delegationProof` SHOULD be a short-lived message,
RECCOMENDED a few minutes to a few hours. 
Once a `delegationProof` is generated,
the client SHOULD be able to sign messages,
without the need for repeated wallet prompts requesting to sign.

#### Delegation Flow:

1. The client generates a new `browserKey`, which is an Ed25519 keypair.
2. The client generates a delegation request to authorize `browserKey` to sign.
3. The user's wallet signs the delegation request and
returns a `delegationProof` with an expiration timestamp, `expiry`.
4. The client stores the `delegationProof`, `browserKey`,
and `expiry`.

A `delegrationProof` could become revoked by the wallet owner or
after the `expiry` time.
If a wallet delegation is revoked, 
clients SHOULD ignore subsequent messages from the revoked delegation key.

### Moderation & Permissions

A post MAY be have moderation message types assigned by the channel admin.
The moderation types include:

- `HIDE` : To hide a post or comment.
- `REMOVE` : To permanently remove a post or comment.
- `PIN` : To pin a post to the top of a channel feed or pin a comment to the top of a thread.
- `UNPIN` : To remove a `PIN` from a post feed or comment thread.
- `CHANGE_OWNERSHIP` : Change the `author` of a post or comment.

Moderation messages MUST be signed by an admin, 
which recognized the `author` of the channel. 
Clients SHOULD validate the admin before applying moderation events locally.

### Relevance Score

A post can gain better visibility on the forum channel and
the forum's search through the content relevance score.
Clients with verified wallet identities MUST be favored over an anonymous session identity.

There are a few RECCOMENDED areas that collect points when calculating the relevance score of a post:

Basic points include the activities that each user is able to engage in.

- A channel has a score value of 15
- Each post within a channel has a score value of 10
- A base value if comments are present within a post boosts the relevance score by a value of 5

Engagement points include the different user activities for each post or comment.

- Each wallet delegation upvote adds a score value of 1.
- Each individual comment adds a score value of 0.5.
- The total number of posts multiplied by 0.5.
The total number of upvotes multiplied by 0.1.
These two values are added together.

For identity verification points,
participants of posts or comments that use wallet-based identities,
including an optional ENS,
the score is boosted over the anonymous identities.
If a participant has a verified ENS and a verified connected wallet,
only the ENS multiplier SHOULD be applied.

- Participants who have a verified ENS name gain a value multiplier of 1.25(25%).
- For wallet connect participant the multiplier is 1.1(10%).
- For verified upvote participants the multiplier is 0.1.
- For verified comment participants the multiplier is 0.05.

There is a time decay that reduces the relevance score over time.
The older a post or comment was made the lower its score.

$$
\text{timeDecayMultiplier} = e^{-\lambda \cdot \text{daysOld}}
$$

Where $$\( -\lambda \)$$ is the time-decay rate per day.

There SHOULD be a moderation penalty that reduces the score when a post or
comment is moderated with a value of 0.5(50%).
This penalty is applied once a post is `HIDDEN`, `REMOVED` or `FLAGGED` by a moderator.

$$ 
\text{moderationPenalty} = \begin{cases} 0.5, & \text{if moderated} \\
1,   & \text{otherwise} \end{cases}
$$

Below is the final relevance score based on the RECCOMENDED points above:

$$
\text{Total RelevanceScore} = (\text{basic} + \text{engagement} + \text{verifiedUpvote})
\cdot (1 + \text{verifyIdentity}) \cdot \text{timeDecay} \cdot \text{moderationPenalty}
$$

## Copyright

Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).

## References
- [10/WAKU2](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/10/waku2.md)
- [14/WAKU-MESSAGES](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/14/message.md)
- [23/WAKU2-TOPICS](https://github.com/vacp2p/rfc-index/blob/main/waku/informational/23/topics.md)
-