farcaster-auth

Setup

First, ensure that the following are installed globally on your machine:

• Node.js 16+
• Yarn

yarn add @zachterrell57/farcaster-auth

Usage

Generating a signature

import { generateSignature, verifyUser } from '@zachterrell57/farcaster-auth';

const credentials = generateSignature();

const signature = credentials.signature;
const address = credentials.address;

Casting the signature to Farcaster

It is now up to the user to cast the signature to Farcaster. Until v2 of the protocol, it is probably easiest to post from the Merkle Manufactory app. Clients can help the user achieve this by helping them copy the signature to the clipboard, and providing an Open Farcaster button that will open the Merkle app for the user. Users should make sure not to edit the signature, as this will result in a failed authentication

This cast might look something like:

Post visibility

If you are worried that the frequency of auth casts from your users might result in clogged timelines, you can alter the auth cast to lead with the app username, e.g. @unloney <auth message>. If the auth cast is the parent cast and you don't follow the mentioned account, then the cast won't appear on your timeline. We can alter the example above to reflect this:

If you wanted to go further, you could even create a specific "auth" account for your app, e.g. @instacasterAuth or @unlonelyAuth and encourage people not to follow these accounts.

Verifying the user

const username = 'username';

const verified = verifyUser(username, address);

Persistence

After the user is verified, the client is free to store this information in any way. Some options include:

• Creating an authed property on a User object in a centralized DB. This will allow the user to log in via a traditional email and password flow (or magic link), which means the user will remain authenticated across devices and sessions
• Using cookies to persist authentication. This will work if the user only wishes to use the client from one device, but will fail if the client is accessed from a different device (as the cookies are device-specific)