A simple login use case using RWW without needing TLS

I was just thinking this could be a possible login use case

1. Go to a site sending your HTTP identity (e.g. via User Header)

2. Site requires authentication so sends a "Challenge" header

3. Using RWW add the following triple to your site

<#me> <somevocab : challenge> "Challenge-String".

4. On update, refresh the page

5. The relying party will check your page for the challenge string, and
when it finds it there, logs you in

This is much like the common automated process where someone will ask you
to 'verify your homepage' by making you add a string.  With POST / PATCH /
PUT technology perhaps it could all be automated allowing login without the
of the relying party having to use TLS.