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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Late to reply to this, but I didn’t see other replies…<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It does not “authenticate” the realm, but if a request arrives for realm good_site.example.com, then a positive assertion will only be provided if the return URL is properly is a part of that that realm (i.e., same name or perhaps a sub-domain thereof). So, there is some checking. A positive assertion will not be returned to bad_site.example.org, for example.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>So, exactly what is the security issue? I’ll not deny there is one, but it is not clear to me.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I took a brief look at your paper and it seemed to suggest that users might be duped by similar-looking domain names, but that is human error, not protocol error. Is that the point?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Paul<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt'><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> openid-general-bounces@lists.openid.net [mailto:openid-general-bounces@lists.openid.net] <b>On Behalf Of </b>Francisco Corella<br><b>Sent:</b> Wednesday, December 22, 2010 2:13 PM<br><b>To:</b> openid-general@lists.openid.net<br><b>Subject:</b> [OpenID] security weakness regarding authentication of the relying party<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0><tr><td valign=top style='padding:0in 0in 0in 0in'><p class=MsoNormal style='margin-bottom:12.0pt'>Hi all,<br><br>There is a security weakness in OpenID which may be already<br>known but is not discussed in the security considerations<br>section of the specification. It hinges on the fact that<br>the OpenID provider does not authenticate the relying party.<br>I discuss the issue in detail in a <a href="http://www.pomcor.com/whitepapers/PKAuth.pdf">paper</a>.<br><br>OAuth solves this problem in theory by requiring the OAuth<br>client (the relying party) to register with the OAuth<br>server. But Google and Yahoo allow unregistered<br>applications, so the problem remains. Btw compulsory<br>registration is a bad idea: imagine a situation where<br>a social site becomes dominant, social login via that site<br>becomes the de facto authentication standard on the Web,<br>every application has to register with the site, and the<br>site can kill any application by revoking its registration.<br><br>The <a href="http://www.pomcor.com/whitepapers/PKAuth.pdf">paper</a> proposes a solution to all this. Thanks in<br>advance for any comments.<br><br>-- Francisco<o:p></o:p></p></td></tr></table><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p></div></div></body></html>