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I like the text that's there, but let's add this to cover the other (in my view, more common) case:
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<div>"Another option, often useful for clients that are web servers or native applications, is to store the value of the nonce in a protected store local to the client, away from the user agent. This value can be retrieved from the store when the end user returns
to the client via the redirect_uri and used when validating the id_token."
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<div> -- Justin</div>
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<div>On Nov 13, 2013, at 10:16 PM, Mike Jones <<a href="mailto:Michael.Jones@microsoft.com">Michael.Jones@microsoft.com</a>> wrote:</div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">If you want to propose specific text changes, we can look at them. Otherwise, I think we’re good.<o:p></o:p></span></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> -- Mike<o:p></o:p></span></div>
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<b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; ">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; "><span class="Apple-converted-space"> </span>John Bradley [mailto:ve7jtb@<a href="http://ve7jtb.com">ve7jtb.com</a>]<span class="Apple-converted-space"> </span><br>
<b>Sent:</b><span class="Apple-converted-space"> </span>Wednesday, November 13, 2013 12:40 PM<br>
<b>To:</b><span class="Apple-converted-space"> </span>Brian Campbell<br>
<b>Cc:</b><span class="Apple-converted-space"> </span>George Fletcher; Mike Jones;
<a href="mailto:openid-specs-ab@lists.openid.net">openid-specs-ab@lists.openid.net</a><br>
<b>Subject:</b><span class="Apple-converted-space"> </span>Re: [Openid-specs-ab] Nonce value suggestion for the Implicit Flow<o:p></o:p></span></div>
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<o:p> </o:p></div>
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That looks good.<o:p></o:p></div>
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<o:p> </o:p></div>
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One question is if we want to also say the nonce value may be stored as part of the session state on the client (webserver). <o:p></o:p></div>
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<o:p> </o:p></div>
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Adding too many options may just confuse people though.<o:p></o:p></div>
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<o:p> </o:p></div>
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John B.<o:p></o:p></div>
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On Nov 13, 2013, at 11:38 AM, Brian Campbell <<a href="mailto:bcampbell@pingidentity.com" style="color: purple; text-decoration: underline; ">bcampbell@pingidentity.com</a>> wrote:<o:p></o:p></div>
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"a random value as an HttpOnly a session cookie" -> remove the "a" after HttpOnly?<o:p></o:p></div>
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<o:p> </o:p></p>
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On Wed, Nov 13, 2013 at 11:35 AM, George Fletcher <<a href="mailto:gffletch@aol.com" target="_blank" style="color: purple; text-decoration: underline; ">gffletch@aol.com</a>> wrote:<o:p></o:p></div>
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<span style="font-family: Helvetica, sans-serif; ">I'll let John quibble over the specifics :) ... but it looks good to me. Thanks, George</span><o:p></o:p></p>
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On 11/13/13 1:30 PM, Mike Jones wrote:<o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Please review the new text at<span class="Apple-converted-space"> </span><a href="http://openid.bitbucket.org/openid-connect-core-1_0.html#NonceNotes" target="_blank" style="color: purple; text-decoration: underline; ">http://openid.bitbucket.org/openid-connect-core-1_0.html#NonceNotes</a>,
which is where the implementation suggestions for the nonce parameter have been moved.</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> -- Mike</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><o:p></o:p></div>
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<b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; ">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; "><span class="Apple-converted-space"> </span><a href="mailto:openid-specs-ab-bounces@lists.openid.net" target="_blank" style="color: purple; text-decoration: underline; ">openid-specs-ab-bounces@lists.openid.net</a><span class="Apple-converted-space"> </span>[<a href="mailto:openid-specs-ab-bounces@lists.openid.net" target="_blank" style="color: purple; text-decoration: underline; ">mailto:openid-specs-ab-bounces@lists.openid.net</a>]<span class="Apple-converted-space"> </span><b>On
Behalf Of<span class="Apple-converted-space"> </span></b>Brian Campbell<br>
<b>Sent:</b><span class="Apple-converted-space"> </span>Wednesday, October 30, 2013 9:00 AM<br>
<b>To:</b><span class="Apple-converted-space"> </span>John Bradley<br>
<b>Cc:</b><span class="Apple-converted-space"> </span><a href="mailto:openid-specs-ab@lists.openid.net" target="_blank" style="color: purple; text-decoration: underline; ">openid-specs-ab@lists.openid.net</a><br>
<b>Subject:</b><span class="Apple-converted-space"> </span>Re: [Openid-specs-ab] Nonce value suggestion for the Implicit Flow</span><o:p></o:p></div>
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The nonce is a different approach to protecting against things like replay prevention but doesn't have the same scaling implications as tracking token ids. Which is nice.<o:p></o:p></div>
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On Wed, Oct 30, 2013 at 4:13 AM, John Bradley <<a href="mailto:ve7jtb@ve7jtb.com" target="_blank" style="color: purple; text-decoration: underline; ">ve7jtb@ve7jtb.com</a>> wrote:<o:p></o:p></div>
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The nonce is opaque to the AS, it is sent by the client and validated by the client. It binds the signed id_token to something in the user's browser session. This is critical to prevent attacks on the implicit flow, where the redirect_uri is not sent to
the token endpoint for validation. It is not required for the "code" flow. In the hybrid flows it needs to be used to validate the id_token presented in the front channel as well, as the client may be using the id_token before exchanging code at the token
endpoint, and discovering an attack.<o:p></o:p></div>
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I think it also prevents some attacks against code interception that checking the redirect_uri wouldn't so in a high loa deployment I would check both nonce and the redirect_uri.<o:p></o:p></div>
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Are you asking about "jti" in the assertion used to authenticate the client to the token endpoint?<o:p></o:p></div>
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On Oct 30, 2013, at 1:44 AM, Anthony Nadalin <<a href="mailto:tonynad@microsoft.com" target="_blank" style="color: purple; text-decoration: underline; ">tonynad@microsoft.com</a>> wrote:<o:p></o:p></div>
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<o:p> </o:p></p>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">I’m not seeing how you are dealing with duplicate nonces as this can be a scaling issue when dealing with millions of requests, the nonces need better advice</span><o:p></o:p></div>
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<a name="14252bf9530978a2_14208dc46cdfd917__MailE"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span></a><o:p></o:p></div>
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<b><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">From:</span></b><span style="font-size: 11pt; font-family: Calibri, sans-serif; "> <a href="mailto:openid-specs-ab-bounces@lists.openid.net" target="_blank" style="color: purple; text-decoration: underline; ">openid-specs-ab-bounces@lists.openid.net</a><span class="Apple-converted-space"> </span>[<a href="mailto:openid-specs-ab-bounces@lists.openid.net" target="_blank" style="color: purple; text-decoration: underline; ">mailto:openid-specs-ab-bounces@lists.openid.net</a>] <b>On
Behalf Of </b>John Bradley<br>
<b>Sent:</b> Tuesday, October 29, 2013 7:33 PM<br>
<b>To:</b> Mike Jones<br>
<b>Cc:</b> <a href="mailto:openid-specs-ab@lists.openid.net" target="_blank" style="color: purple; text-decoration: underline; ">openid-specs-ab@lists.openid.net</a><br>
<b>Subject:</b> Re: [Openid-specs-ab] Nonce value suggestion for the Implicit Flow</span><o:p></o:p></div>
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You want to store the random value and send the hash. Saving the hash is not secure unless it is signed. <o:p></o:p></div>
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The idea is to force an attacker to compute a plaintext for the hash (hard to impossible depending on length) in order to be able to present the response from the AS.<o:p></o:p></div>
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<o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">For case 1: The Client can generate a random value with sufficient entropy and store that value in local storage. This value is then hashed to produce a nonce value.
The hashed value could optionally be truncated to a sufficient number of bits (such as 128) before use. </span><o:p></o:p></div>
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On Oct 29, 2013, at 9:40 PM, Mike Jones <<a href="mailto:Michael.Jones@microsoft.com" target="_blank" style="color: purple; text-decoration: underline; "><span style="color: purple; ">Michael.Jones@microsoft.com</span></a>> wrote:<o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Here’s an attempt at simplifying George’s text.</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">For case 1: The Client can generate a random value with sufficient entropy and store a cryptographic hash (such as SHA-256) of that value in local storage. The hashed
value could optionally be truncated to a sufficient number of bits (such as 128) before use. The stored value is used as the nonce value.</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">For case 2: The Client can generate a random value with sufficient entropy and store that value as an HttpOnly session cookie. A cryptographic hash (such as SHA-256)
of the cookie value (or a truncation of the hash value to a sufficient number of bits) is used as the nonce value.</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Am I correct that the cryptographic hash function is used to spread the entropy present in the random value generated throughout the nonce value in both cases?</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Comments?</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> -- Mike</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><o:p></o:p></div>
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<b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; ">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; "> Richer, Justin P. [<a href="mailto:jricher@mitre.org" target="_blank" style="color: purple; text-decoration: underline; "><span style="color: purple; ">mailto:jricher@mitre.org</span></a>] <br>
<b>Sent:</b> Saturday, October 26, 2013 11:33 AM<br>
<b>To:</b> George Fletcher<br>
<b>Cc:</b> John Bradley; Mike Jones; <a href="mailto:openid-specs-ab@lists.openid.net" target="_blank" style="color: purple; text-decoration: underline; "><span style="color: purple; ">openid-specs-ab@lists.openid.net</span></a><br>
<b>Subject:</b> Re: [Openid-specs-ab] Nonce value suggestion for the Implicit Flow</span><o:p></o:p></div>
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<span style="font-family: Helvetica, sans-serif; ">I don't know where the best place is to provide this guidance. If we have a "validating the ID Token" sub-section in the new ID Token section, then maybe it would best fit there.</span><o:p></o:p></div>
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+1 to this idea with a cross link from the nonce definition.<o:p></o:p></div>
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-- Justin<o:p></o:p></div>
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On Oct 25, 2013, at 6:17 AM, George Fletcher <<a href="mailto:gffletch@aol.com" target="_blank" style="color: purple; text-decoration: underline; "><span style="color: purple; ">gffletch@aol.com</span></a>> wrote:<o:p></o:p></div>
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<span style="font-family: Helvetica, sans-serif; ">If we are going to give guidance, then we really need to give guidance for two different use cases...<br>
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1. The "client" will validate the response locally in the browser<br>
2. The "client" will validate the response at it's server (even though it's using the implicit flow)<br>
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For use case 1: One method to achieve this is for the client to generate a random string with sufficient entropy and store a SHA-1 hash of the string in local storage. Then use the SHA-1 hash of the random string as the value of the nonce parameter. To validate
the nonce on receipt of the ID Token, extract the nonce from the ID Token and compare it to the stored SHA-1 hash in local storage.<br>
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For use case 2: One method to achieve this is for the backend server to use a SHA-1 hash of the "clients" protected session cookie as the value of the nonce parameter when constructing the AuthorizationRequest. Note that the Session cookie SHOULD be protected
(restricted to SSL and not readable by JavaScript) for this method. To validate the ID Token at the server, the server calculates a SHA-1 hash of the Session cookie value and compares that to the nonce value in the ID Token.<br>
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I don't know where the best place is to provide this guidance. If we have a "validating the ID Token" sub-section in the new ID Token section, then maybe it would best fit there.<br>
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Thanks,<br>
George</span><o:p></o:p></p>
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On 10/24/13 7:16 PM, John Bradley wrote:<o:p></o:p></div>
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We want the implicit flow to validate nonce, it would be better to have some reasonable advice for using HTML local storage rather than session cookies.<o:p></o:p></div>
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On 2013-10-24, at 3:44 PM, Mike Jones <<a href="mailto:Michael.Jones@microsoft.com" target="_blank" style="color: purple; text-decoration: underline; "><span style="color: purple; ">Michael.Jones@microsoft.com</span></a>> wrote:<o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">We could drop it from the Implicit Flow, as it’s already present in the Code Flow. Does that work for people?</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> -- Mike</span><o:p></o:p></div>
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<b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; ">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; "> Richer, Justin P. [<a href="mailto:jricher@" target="_blank" style="color: purple; text-decoration: underline; "><span style="color: purple; ">mailto:jricher@</span></a><a href="http://mitre.org/" target="_blank" style="color: purple; text-decoration: underline; "><span style="color: purple; ">mitre.org</span></a>] <br>
<b>Sent:</b> Thursday, October 24, 2013 12:56 PM<br>
<b>To:</b> Mike Jones<br>
<b>Cc:</b> <a href="mailto:openid-specs-ab@lists.openid.net" target="_blank" style="color: purple; text-decoration: underline; "><span style="color: purple; ">openid-specs-ab@lists.openid.net</span></a><br>
<b>Subject:</b> Re: [Openid-specs-ab] Nonce value suggestion for the Implicit Flow</span><o:p></o:p></div>
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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).<o:p></o:p></div>
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-- Justin<o:p></o:p></div>
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On Oct 24, 2013, at 11:44 AM, Mike Jones <<a href="mailto:Michael.Jones@microsoft.com" target="_blank" style="color: purple; text-decoration: underline; "><span style="color: purple; ">Michael.Jones@microsoft.com</span></a>><o:p></o:p></div>
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wrote:<o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; ">For the Implicit Flow, the “nonce” description contains this text at<a href="http://openid.bitbucket.org/openid-connect-core-1_0.html#ImplicitAuthorizationRequest" target="_blank" style="color: purple; text-decoration: underline; "><span style="color: purple; ">http://openid.bitbucket.org/openid-connect-core-1_0.html#ImplicitAuthorizationRequest</span></a>:</span><o:p></o:p></div>
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<span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif; ">Sufficient entropy MUST be present in the </span><tt style="font-family: 'Courier New'; "><span lang="EN" style="font-size: 10pt; color: rgb(0, 51, 102); ">nonce</span></tt><span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif; "> values
used to prevent attackers from guessing values. <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'; "><span lang="EN" style="font-size: 10pt; color: rgb(0, 51, 102); background-color: yellow; background-position: initial initial; background-repeat: initial initial; ">nonce</span></tt><span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif; background-color: yellow; background-position: initial initial; background-repeat: initial initial; "> parameter.
In that case, the </span><tt style="font-family: 'Courier New'; "><span lang="EN" style="font-size: 10pt; color: rgb(0, 51, 102); background-color: yellow; background-position: initial initial; background-repeat: initial initial; ">nonce</span></tt><span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif; background-color: yellow; background-position: initial initial; background-repeat: initial initial; "> 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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<span style="font-size: 11pt; font-family: Calibri, sans-serif; "> </span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; ">George wrote this about the suggestion in his review:</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; ">“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.”</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Do people agree with him? If so, does someone want to supply specific alternative text to use?</span><o:p></o:p></div>
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<span style="font-size: 11pt; font-family: Calibri, sans-serif; "> -- Mike</span><o:p></o:p></div>
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<span style="font-size: 13.5pt; font-family: Helvetica, sans-serif; ">_______________________________________________<br>
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-- <br>
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<pre style="margin: 0in 0in 0.0001pt; font-size: 10pt; font-family: 'Courier New'; ">Openid-specs-ab mailing list<o:p></o:p></pre>
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<span style="color: rgb(136, 136, 136); ">--<span class="Apple-converted-space"> </span><br>
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