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<div>Thomas,</div>
<div><br>
</div>
<div>If a CRL with lifetime of several hours or several days is acceptable, I do not see why a 'nocheck' OCSP responder's certificate is not acceptable. Their security level are just equal.</div>
<div><br>
</div>
<div>By issuing a short-lived OCSP responder certificate, it does not means you have to regenerate its private key. You can keep use the same key pair until you feel you have to regenerate it or your certificate policies require you to regenerate it.</div>
<div><br>
</div>
<div>Wen-Cheng Wang</div>
<br>
<br>
<br>
-------- 原始郵件 --------<br>
自： Thomas Kopp <thomas.kopp@luxtrust.lu> <br>
日期： <br>
至： 王文正 <wcwang@cht.com.tw>,public@cabforum.org,questions@cabforum.org <br>
主旨： RE: [cabfquest] Question concerning CAB Forum OCSP Requirments <br>
<br>
<br>
<div class="WordSection1">
<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D">Dear Wen-Cheng,</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D">We have well understood the wording of the RFC. However, our goal is to completely avoid issuing responder certificates containing the id-pkix-ocsp-nocheck
extension because even with a short life time of a responder certificate we consider such an approach as an unnecessary lowering of security.
</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D">In addition, I’m not sure whether you are aware what issuance of an OCSP responder certificates within hours means in practice. Such a rule seems a bit far
away from reality because it requires key ceremonies charging a couple responsible people for several hours.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D">Finally, our question concerning the motivation behind the requirement has not been answered yet.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D"> </span></p>
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<span lang="DE-LU" style="font-size:8.0pt; font-family:"Arial","sans-serif"; color:#1F497D">Bescht Gréiss, meilleures salutations, mit freundlichen Grüßen, with best regards,</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"">
</span><span style="font-size:10.0pt; font-family:"MS UI Gothic","sans-serif"">王文正</span><span style="font-size:10.0pt; font-family:"Tahoma","sans-serif""> [mailto:wcwang@cht.com.tw]
<br>
<b>Sent:</b> Méindeg 27 Oktober 2014 15:49<br>
<b>To:</b> Thomas Kopp; public@cabforum.org; questions@cabforum.org<br>
<b>Subject:</b> Re: [cabfquest] Question concerning CAB Forum OCSP Requirments</span></p>
</div>
</div>
<p class="MsoNormal"> </p>
<div>
<p class="MsoNormal">Thomas,</p>
</div>
<div>
<p class="MsoNormal"> </p>
</div>
<div>
<p class="MsoNormal">The CAB forum does not impose any high risk on trust service providers or relying parties. You misquote the text, please read the full paragraph in the RFC.</p>
</div>
<div>
<p class="MsoNormal"> </p>
</div>
<div>
<p class="MsoNormal">The intention of the text you highlighted in yellow color is to remind CAs that it is dangrous if the lifetime of a 'nocheck' OCSP responder's certificate is too long. That is why the subsequent text says "CAs may choose to issue this
type of certificate with a very short lifetime and renew it frequently."</p>
</div>
<div>
<p class="MsoNormal"> </p>
</div>
<div>
<p class="MsoNormal">The RFC is intent to tell CAs that it will be safe if they keep the lifetime of a 'nocheck' OCSP responder's certificate very short. In a typical implemention, the lifetime might range from several hours to several days.</p>
</div>
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<p class="MsoNormal"> </p>
</div>
<div>
<p class="MsoNormal">Wen-Cheng Wang</p>
</div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
<br>
<br>
-------- <span style="font-family:"MS Mincho"">原始郵件</span> --------<br>
<span style="font-family:"MS Mincho"">自：</span> Thomas Kopp <<a href="mailto:thomas.kopp@luxtrust.lu">thomas.kopp@luxtrust.lu</a>>
<br>
<span style="font-family:"MS Mincho"">日期：</span> <br>
<span style="font-family:"MS Mincho"">至：</span> <a href="mailto:public@cabforum.org,questions@cabforum.org">
public@cabforum.org,questions@cabforum.org</a> <br>
<span style="font-family:"MS Mincho"">主旨：</span> [cabfquest] Question concerning CAB Forum OCSP Requirments
<br>
<br>
</p>
<div>
<p class="MsoNormal" style="">Dear all,</p>
<p class="MsoNormal" style=""> </p>
<p class="MsoNormal" style="">Can you please clarify the subsequent point?</p>
<p class="MsoNormal" style=""> </p>
<p class="MsoNormal" style="">In the CAB baseline requirements <a href="https://cabforum.org/wp-content/uploads/Baseline_Requirements_V1_1_9.pdf" target="_BLANK">
https://cabforum.org/wp-content/uploads/Baseline_Requirements_V1_1_9.pdf</a> section 13.2.5 imposes the id-pkix-ocsp-nocheck extension in the case of an authorized responder scenario.</p>
<p class="MsoNormal" style=""> </p>
<p class="MsoNormal" style="">By contrast, RFC 2560 and the successor RFC 6960 stipulate (cf. section 4.2.2.2.1):</p>
<pre>A CA may specify that an OCSP client can trust a responder for the</pre>
<pre> lifetime of the responder's certificate. The CA does so by</pre>
<pre> including the extension id-pkix-ocsp-nocheck. This SHOULD be a</pre>
<pre> non-critical extension. The value of the extension SHALL be NULL.</pre>
<pre> <span style="background:yellow">CAs issuing such a certificate should realize that a compromise of</span></pre>
<pre><span style="background:yellow"> the responder's key is as serious as the compromise of a CA key</span></pre>
<pre><span style="background:yellow"> used to sign CRLs, at least for the validity period of this</span></pre>
<pre><span style="background:yellow"> certificate</span>….</pre>
<p class="MsoNormal" style=""> </p>
<p class="MsoNormal" style="">How can CAB Forum impose such a requirement, which imposes to trust service providers such a high security risk?</p>
<p class="MsoNormal" style=""> </p>
<p class="MsoNormal" style="">Please provide us a reasonable explanation for this particular requirement. Please note that we would not want to hear any technical reasoning like possible “self-looping” during OCSP responder certificate status checking, because
such issues can perfectly be addressed without having to lower security.</p>
<p class="MsoNormal" style=""> </p>
<p class="MsoNormal" style="margin-right:14.05pt; text-autospace:none"><span lang="DE-LU" style="font-size:8.0pt; font-family:"Arial","sans-serif"">Bescht Gréiss, meilleures salutations, mit freundlichen Grüßen, with best regards,</span></p>
<p class="MsoNormal" style="margin-right:14.05pt; text-autospace:none"><b><span lang="DE-LU" style="font-family:"Arial","sans-serif"; color:#C00000"> </span></b></p>
<p class="MsoNormal" style="margin-right:14.05pt; text-autospace:none"><b><span lang="EN-GB" style="font-family:"Arial","sans-serif"; color:#C00000">Thomas KOPP
</span></b></p>
<p class="MsoNormal" style="margin-right:14.05pt; text-autospace:none"><span lang="EN-GB" style="font-size:8.0pt; font-family:"Arial","sans-serif"">Head of Information Technologies</span></p>
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