<div dir="ltr">I have been shifting my identity to my own i-name, and adding several authentication SEPs so that regardless of which RP I sign into, a supported OP ought to be found in my list (if the RP were to use a whitelist for example). In theory, it's really cool. I can log in as =Arnott anywhere (that takes OpenID) and my CanonicalID is used so my identity is secure for my whole life. Great... in theory.<br>
<br>Here are some of the harsh realities I've encountered while trying to live in this ideal situation:<br><ol><li>The RP selects the wrong OP from the XRDS document (it supports any/all of the OPs, but chooses the first listed one rather than the one with the best priority rating).</li>
<li>The RP attempts authentication against one of my OPs (whether it's my preferred one or not) and fails, whether it's a discovery failure, an assertion verification failure, or whatever.</li><li>Although many RPs can authenticate me as =Arnott, the ones that can't I try <a href="http://blog.nerdbank.net">http://blog.nerdbank.net</a>, which includes both an XRDS refererence and the standard OpenID LINK tags. If this succeeds, now I've got to remember which sites I've logged into as =Arnott vs. <a href="http://blog.nerdbank.net">blog.nerdbank.net</a>. If this fails, then I can choose to either surrender my attempt at using my own personalized identifier and start trying my individual OP-assigned identifiers, or just give up and leave the RP.<br>
</li><li>Upon successful authentication, the RP incorrectly stores my user-supplied identifier (=Arnott) instead of my claimed identifier (=!9B72.7DD1.50A9.5CCD). Since I have no/little way of realizing this, I naively believe that my identity on this site is secure, but when I eventually surrender my =Arnott i-name for another one but keep my CanonicalID, the site doesn't recognize me as the same person, and worse, someone else assumes my identity.</li>
<li>Many RPs choose to use their own home-spun minimal implementation of OpenID that is full of security holes (I've seen plenty). As a logging in user, I have no way to know whether this is a decent implementation of OpenID that I'm logging into or not. If I doubt it at all, then I must assume that anyone else can spoof my identity on this site by exploiting one of the many bugs common in these home spun implementations.</li>
</ol>Correctly processing an XRDS document in a fully XRDS spec-compliant way is no small task, and I'd wager that most or all of the OpenID libraries do not do it perfectly. This means that any user trying to make the most of OpenID will likely be unable to log into some RP web sites, or perhaps may be able to but be unaware that the RP incorrectly interpreted the XRDS doc and stored something wrong about his identity. <br>
<b><br>Suggestions</b><br>It seems to me that if an RP doesn't want to risk losing visitors due to their unexpected or perhaps buggy identifiers/OPs, an RP should probably have a list of known-compatible OPs on any authentication error page it might display.<br>
I have a suggestion for the other problem(s), but I'm still working out details. I may propose it to this list soon.<br><br>In the meantime, does anyone else have thoughts regarding how to help solve these problems? Obviously, "implement the spec correctly" is the trivial answer. I'm looking for ideas on how to <a href="http://blog.nerdbank.net/2008/04/argument-for-extra-dependency-of.html">promote reuse of libraries</a> rather than home-spun implementations, and how to assure users that the right things are happening behind the scenes at the RP so that he/she can trust the site.<br>
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