B4J Code Snippet Web3X - Login/Auth with Metamask example

I've been using the Web3X library these past days and wonder how could it be used for authentication with Metamask. I put together this example but is not near perfect, I don't recommend using it in production since there are a lot of things I don't understand yet, but if your goal is to learn you could run this code.

I took ideas from many sites to understand what should be done, mainly the web3js docs: https://web3js.readthedocs.io/en/v1.5.2/

The code flow looks like this (source):
toptal-blog-image-1522395353253-70fb1c40e9527154c2774507b63eac63.png

You must run the b4j server and access it by localhost, otherwise the Metamask wallet will not be detected if you just open the index.html.

The index.html file is just a button on the top left corner of the screen. When pressed we try to connect to the wallet, then get a random message from the server, sign the message and return it for verification, if passed, we get a token which will allow for fast authentication.

The attached screenshots show the process from start to finish.

Disclaimer: After reading the permissions the Metamask chrome extension requires, I don't known how safe it is. For transparency, I created a VM running ubuntu just to play around with crypto apps, I do not run them on my main computer.
 

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