How could one login to the Steem blockchain using his Google/FB/etc account?

One of the main obstacles for Steem app developers and wide adoption from the general public is the cumbersome login process.

Today, a user must enter a 50 character string consisting of a random, case sensitive combination of letters and digits, such as:

5sdlMF23flSFj42fl2r2fglGj23585DgmGLF956mMGElgepg3g

While it is a cumbersome process to input such a token on a desktop computer, it is an even more frustrating task on a mobile device.

As a result many users are left frustrated by the process and do not even pass the initial step of logging in.

On the other hand it is a reality of modern life that most people expect to be able to authenticate themselves with their favourite apps through mainstream content providers and social networks, such as Google and Facebook.

This indirect authentication/authorization usually involves the OAuth2 mechanism.

Assuming that a Steem user would agree to store his posting key on a third party secure server (Steem Posting Key Server), how could an authorization scheme be implemented between the app, the authorization server (e.g. Google) and the resource server (Steem Posting Key Server) to ease the process of signing in on the Steem blockchain using the posting key?

StemQ Notice: This post was originally submitted on StemQ.io, a Q&A application for STEM subjects powered by the Steem blockchain.