I've designed an API for this and started working on it since I got a Yubikey Neo in the past few weeks, if you or anyone is interested. I'm focusing on UX spec

I've designed an API for this and started working on it since I got a Yubikey Neo in the past few weeks, if you or anyone is interested. I'm focusing on UX specifically. My design has a REST endpoint that runs locally, and a JS client/SDK then connects to it on a known endpoint. My "MVP" version is to have the user running an interface with the request queue in a separate tab, and the server always at a fixed localhost:port endpoint. The client page would then issue a REST request that hangs until the user responds to the request in the separate tab. This would conceivably work as a browser plugin as well since I'm planning to write it in JS for Node--basically the server logic would instead live in the plugin and the SDK would check for presence of the plugin before making a REST call. IMO the advantage of making it a REST endpoint though, is protecting private keys from whatever else might be going on in the browser process(es)--based on my own worst-case on assumptions, unsure if it's actually an issue with the plugin architectures. I'm an aspiring interaction/UX designer so that is the aspect I am focusing on, and my motivation is that I am personally starting to use GPG with a Yubikey + offline master. So yea, collaborators hit me up, especially if you're in SF.