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I'm actually in favor of dropping this example, or else providing it in a list of alternatives. The important thing is that the client can validate the exact value of the nonce parameter on its way back through, the mechanics of how that happens are client
specific (but we can provide simple guidance).
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<div> -- Justin</div>
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<div>On Oct 24, 2013, at 11:44 AM, Mike Jones <<a href="mailto:Michael.Jones@microsoft.com">Michael.Jones@microsoft.com</a>></div>
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For the Implicit Flow, the “nonce” description contains this text at<a href="http://openid.bitbucket.org/openid-connect-core-1_0.html#ImplicitAuthorizationRequest" style="color: purple; text-decoration: underline; ">http://openid.bitbucket.org/openid-connect-core-1_0.html#ImplicitAuthorizationRequest</a>:<o:p></o:p></div>
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<span lang="EN" style="font-family: Verdana, sans-serif; ">Sufficient entropy MUST be present in the<span class="Apple-converted-space"> </span></span><tt style="font-family: 'Courier New'; color: rgb(0, 51, 102); "><span lang="EN" style="font-size: 12pt; ">nonce</span></tt><span lang="EN" style="font-family: Verdana, sans-serif; "><span class="Apple-converted-space"> </span>values
used to prevent attackers from guessing values.<span class="Apple-converted-space"> </span><span style="background-color: yellow; background-position: initial initial; background-repeat: initial initial; ">One method to achieve this is to store a random value
as a signed session cookie, and pass the value in the</span></span><tt style="font-family: 'Courier New'; color: rgb(0, 51, 102); "><span lang="EN" style="font-size: 12pt; background-color: yellow; background-position: initial initial; background-repeat: initial initial; ">nonce</span></tt><span lang="EN" style="font-family: Verdana, sans-serif; background-color: yellow; "><span class="Apple-converted-space"> </span>parameter.
In that case, the<span class="Apple-converted-space"> </span></span><tt style="font-family: 'Courier New'; color: rgb(0, 51, 102); "><span lang="EN" style="font-size: 12pt; background-color: yellow; background-position: initial initial; background-repeat: initial initial; ">nonce</span></tt><span lang="EN" style="font-family: Verdana, sans-serif; background-color: yellow; "><span class="Apple-converted-space"> </span>in
the returned ID Token can be compared to the signed session cookie to detect ID Token replay by third parties.</span><o:p></o:p></div>
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<o:p> </o:p></div>
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George wrote this about the suggestion in his review:<o:p></o:p></div>
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“I'm not sure this suggestion makes sense for the implicit flow. The client would need to write a cookie value on the domain of the redirect_uri and the attempt to read it on the return of the implicit flow. Wondering if a local storage example would make more
sense.”<o:p></o:p></div>
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<o:p> </o:p></div>
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Do people agree with him? If so, does someone want to supply specific alternative text to use?<o:p></o:p></div>
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<o:p> </o:p></div>
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-- Mike<o:p></o:p></div>
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<o:p> </o:p></div>
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