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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">This was one of the two open issues discussed on the 4-Mar-13 working group call. You were on that call, according to the minutes. We had a fairly extensive
discussion about the meaning of “acr” and the right way to return information about authentication methods used. Originally the request was to allow multi-valued “acr” values. There was a use case where an implementation wanted to communicate the actual
methods used such as “password”, “OTP”, “code in text message”, etc. and I’d originally advocated for letting “acr” be multi-valued, just like PAPE did. John, Tony, and I think you convinced us that that conflating classes with methods would create more problems
than it would solve and that it was better to define an optional claim for returning an array of methods used, when needed.<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">On that call we also deleted the LoA values “1”, “2”, “3”, and “4” since as part of that discussion, it came up that they are prohibited by RFC 6711. Instead,
we replaced the example values used with real values from InCommon - urn:mace:incommon:iap:bronze and urn:mace:incommon:iap:silver.<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 don’t think that we should require “acr” when “amr” is used, because there may not be a class, even though there are methods. It depends upon the business
context in which the parties are communicating. Like “acr”, “amr” is only useful when the values are understood by both parties. Nonetheless, it’s better to have a standard claim for these methods than to have everyone make up a different one. This kind
of information is used in practice, in some contexts.<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"> -- Mike<o:p></o:p></span></p>
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<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-specs-ab-bounces@lists.openid.net [mailto:openid-specs-ab-bounces@lists.openid.net]
<b>On Behalf Of </b>Nat Sakimura<br>
<b>Sent:</b> Friday, May 31, 2013 4:53 PM<br>
<b>To:</b> Torsten Lodderstedt<br>
<b>Cc:</b> OpenId Connect List<br>
<b>Subject:</b> Re: [Openid-specs-ab] amr vs acr<o:p></o:p></span></p>
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<p class="MsoNormal">s/<span style="font-size:10.5pt;font-family:"Arial","sans-serif""> where acr gives more context to the values of acr. / where acr gives more context to the values of amr. /</span><o:p></o:p></p>
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<p class="MsoNormal">2013/6/1 Nat Sakimura <<a href="mailto:sakimura@gmail.com" target="_blank">sakimura@gmail.com</a>><o:p></o:p></p>
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<p class="MsoNormal">I suppose you mean amr, not acm. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I actually was not aware of amr till now. It seems it was a fairly quick decision made between March 4 and 6. <o:p></o:p></p>
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<p class="MsoNormal">See <a href="https://bitbucket.org/openid/connect/issue/789/make-acr-claim-values-be-arrays-of-acr" target="_blank">https://bitbucket.org/openid/connect/issue/789/make-acr-claim-values-be-arrays-of-acr</a><o:p></o:p></p>
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<p class="MsoNormal">At the time, I was so busy managing JICS 2013, so it went unnoticed for me. <o:p></o:p></p>
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<p class="MsoNormal">I also searched through the list archive, but I cannot find the topic in it. There is no record of the decision on the call notes either. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Mike, could you point us to the record how the WG decision was reached? <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Apparently, amr is the list of authentication methods, while acr is the indicator of the identity proofing and authentication quality. <o:p></o:p></p>
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<p class="MsoNormal">i.e., amr is just the list of such things like "password", "otp", etc. while acr is "InCommons Silver", "ISO29115 LoA 3", etc. <o:p></o:p></p>
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<p class="MsoNormal">Personally, I do not see much value in amr since it does not indicate any quality information. It may even be harmful when used without context in the sense that it may create sense of false security to the relying parties. For example,
"otp" by itself does not mean it is secure. An OTP system with badly managed seed will generate a predictable sequence of "one time passwords", which is not secure at all. It would only be meaningful when there is an assurance that the system is properly managed.
In this respect, amr may be meaningful as an auxiliary information only when it is used with acr, where acr gives more context to the values of acr. <o:p></o:p></p>
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<p class="MsoNormal">I might want to require acr if amr is used, or drop amr, but that is only my personal opinion. <o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
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<p class="MsoNormal">2013/6/1 Torsten Lodderstedt <<a href="mailto:torsten@lodderstedt.net" target="_blank">torsten@lodderstedt.net</a>><o:p></o:p></p>
<p class="MsoNormal">Hi,<br>
<br>
could someone please describe me the difference between the id token members acr and acm? From my understanding, they are just the same. I'm also interested to learn why the authorization request allows to specify multiple acrs but does not support to specify
any authentication method (via acm). Additionally, why is there no way to indicate more than one acr in the id token?<br>
<br>
Thanks in advance,<br>
Torsten.<br>
_______________________________________________<br>
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<a href="mailto:Openid-specs-ab@lists.openid.net" target="_blank">Openid-specs-ab@lists.openid.net</a><br>
<a href="http://lists.openid.net/mailman/listinfo/openid-specs-ab" target="_blank">http://lists.openid.net/mailman/listinfo/openid-specs-ab</a><o:p></o:p></p>
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<p class="MsoNormal"><span class="hoenzb"><span style="color:#888888">-- </span></span><span style="color:#888888"><br>
<span class="hoenzb">Nat Sakimura (=nat)<o:p></o:p></span></span></p>
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<p class="MsoNormal"><span style="color:#888888">Chairman, OpenID Foundation<br>
<a href="http://nat.sakimura.org/" target="_blank">http://nat.sakimura.org/</a><br>
@_nat_en</span><o:p></o:p></p>
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<p class="MsoNormal">-- <br>
Nat Sakimura (=nat)<o:p></o:p></p>
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<p class="MsoNormal">Chairman, OpenID Foundation<br>
<a href="http://nat.sakimura.org/" target="_blank">http://nat.sakimura.org/</a><br>
@_nat_en<o:p></o:p></p>
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