I have planned a very similar thing. I'll probably have it in my custom keyboard's firmware once I'm done building it. The idea is one or more "master" passwo

I have planned a very similar thing. I'll probably have it in my custom keyboard's firmware once I'm done building it. The idea is one or more "master" password(s) that can be stored in keyboard's RAM (so you don't need to type them every time; and yet you still never need to input it into your computer at all!), then a short memorable site-specific "password" (could be as simple as the site's name) plus a prefix/postfix that adjusts the output to work around different services' fucked up password rules. I might also make a completely offline device for this in case I need to "look up" a password without actually typing it into a computer. I don't need to write any crypto for this, just use a well known and secure KDF / hash.