<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Yes the server needs to treat it as unique. The client should make it unique per message but it is probably OK to use it over a limited number of messages, though clients don't send that many authorization requests to have reusing them be a significant saving.<div><br></div><div><br><div><div>On 2013-07-29, at 8:41 AM, Torsten Lodderstedt <<a href="mailto:torsten@lodderstedt.net">torsten@lodderstedt.net</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><meta http-equiv="content-type" content="text/html; charset=utf-8"><div dir="auto"><div>Is this secret intended for one-time use only?</div><div><br>Am 29.07.2013 um 08:29 schrieb Nat Sakimura <<a href="mailto:sakimura@gmail.com">sakimura@gmail.com</a>>:<br><br></div><blockquote type="cite"><div dir="ltr">I have thought of that, and I do not think so. <div>Adding salt amounts to expanding the entropy of the input string. </div><div>So, having enough bit length in the transient secret to start with has the same effect. </div>
<div>Since the validity period of the transient secret is rather short, you cannot do the offline attack. </div><div>The attacker has to have the rainbow table to start with. </div><div><br></div><div>What we want to make sure is that len(tcs) > max_len(available rainbow table). </div>
<div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">2013/7/29 John Bradley <span dir="ltr"><<a href="mailto:ve7jtb@ve7jtb.com" target="_blank">ve7jtb@ve7jtb.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word">Thinking about it overnight we need to also have a salt sent with the hash, to prevent rainbow tables attacks.<div><br><div><div><div class="h5"><div>On 2013-07-28, at 9:39 PM, Nat Sakimura <<a href="mailto:sakimura@gmail.com" target="_blank">sakimura@gmail.com</a>> wrote:</div>
<br></div></div><blockquote type="cite"><div><div class="h5"><div dir="ltr">As some of you knows, passing the code securely to a native app on iOS platform is next to impossible. Malicious application may register the same custom scheme as the victim application and hope to obtain the code, whose success rate is rather high. <div>
<br></div><div>We have discussed about it during the OpenID Conenct Meeting at IETF 87 today, and I have captured the discussion in the form of I-D. It is pretty short and hopefully easy to read. </div><div><br></div><div>
You can find it at: </div><div><br></div><div><a href="https://bitbucket.org/Nat/drafts/src/" target="_blank">https://bitbucket.org/Nat/drafts/src/</a></div><div><br></div><div>Comments are welcome. </div><div><div><br></div>
-- <br>Nat Sakimura (=nat)<div>
Chairman, OpenID Foundation<br><a href="http://nat.sakimura.org/" target="_blank">http://nat.sakimura.org/</a><br>@_nat_en</div>
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</blockquote></div><br></div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br>Nat Sakimura (=nat)<div>Chairman, OpenID Foundation<br><a href="http://nat.sakimura.org/" target="_blank">http://nat.sakimura.org/</a><br>
@_nat_en</div>
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