I think there should be a standard for the web for signing user input. Devs would add tags to elements to say they are to be signed, and there would be an element for the signature. And browsers or a browser extension would verify the signatures.
Keys could be imported by the user, stored with the data they are signing (this would still be an advantage as (so long as the browser/extension is pinning every key it finds) you would know if the admin has started messing with data because the key would change), or stored in a TXT record to associate it with a domain name (goes very well with DNSSEC and decentralised naming systems).
There should be a @w3c working group for this.
Keys could be imported by the user, stored with the data they are signing (this would still be an advantage as (so long as the browser/extension is pinning every key it finds) you would know if the admin has started messing with data because the key would change), or stored in a TXT record to associate it with a domain name (goes very well with DNSSEC and decentralised naming systems).
There should be a @w3c working group for this.
@Hyolobrika Possibly, but if by elements you mean HTML elements, you can already do this with custom elements, data-attributes and a bit of JavaScript.