Allow arbitrary use of keys by MetaMask

Multiple sites now let me use MetaMask to sign a message, like one that proves I'm the owner of my address, but I cannot do this directly. If I could mark a body of text (say this text) and let MetaMask sign it for me (just generate a signature text text, nothing on-chain), I can paste it to my email/website as proof that the owner of this address signed this text. This will be a big step towards making the address/keys the cornerstone of identity 3.0. MetaMask of course will also need to be able to take the signature and verify it against the original text, for the other party.

This can be expanded, when public keys are available, for me to be able to encrypt a message for the owner of a specific address (again, if he published his public key and email), and use regular email, for example, as a safe way to send (encrypted) information. All from within the browser.

Basically just letting users use keys available to them in any way they wish (signing, encrypting, validating or decrypting), directly on texts or files.

Thanks for considering
Danny

The issue names no files, tests, or entry points. Start by narrowing the request into specific signing, verification, encryption, or decryption workflows and agreeing on supported inputs and acceptance criteria; completion would require those criteria to be defined and tested.

Written by the indexing model from the issue text.