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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Why does the entropy have to be in the serial number vs a combination of serial number and date/time bits ?<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> public-bounces@cabforum.org [mailto:public-bounces@cabforum.org]
<b>On Behalf Of </b>Richard Barnes<br>
<b>Sent:</b> Friday, February 26, 2016 6:26 PM<br>
<b>To:</b> Ryan Sleevi <sleevi@google.com><br>
<b>Cc:</b> CABFPub <public@cabforum.org><br>
<b>Subject:</b> Re: [cabfpub] Pre-Ballot 164 - Certificate Serial Number Entropy<o:p></o:p></span></p>
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<p class="MsoNormal">On Fri, Feb 26, 2016 at 6:03 PM, Ryan Sleevi <<a href="mailto:sleevi@google.com" target="_blank">sleevi@google.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Is there a reason for the change from "entropy" to "unpredictable bits"<o:p></o:p></p>
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<p class="MsoNormal">Would you be opposed to "64 bits of random data from a cryptographically strong random number generator"?<o:p></o:p></p>
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<p class="MsoNormal">The concern I have with the language change is that while "entropy" is arguably less ambiguous, I fear "unpredictable bits" will create a situation where a CA says "No one knows our [deterministic] algorithm, therefore it's unpredictable"<o:p></o:p></p>
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<p class="MsoNormal">I admit, I'm not terribly thrilled with my rewrite either, because I don't think it should be required to use an RNG on an HSM, for example (that's arguably overkill), but I do want to make sure that the source of entropy is cryptographically
strong (thus ruling out Microsoft's GUIDs, crappy RNGs, etc)<o:p></o:p></p>
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<p class="MsoNormal">I would prefer this proposal. It provides a specific thing that can be verified (whereas "entropy" and "unpredictable" are vague statistical properties).
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<p class="MsoNormal">--Richard<o:p></o:p></p>
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<p class="MsoNormal">On Fri, Feb 26, 2016 at 1:49 PM, Ben Wilson <<a href="mailto:ben.wilson@digicert.com" target="_blank">ben.wilson@digicert.com</a>> wrote:<o:p></o:p></p>
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<p>For discussion:<o:p></o:p></p>
<p><b>Pre-Ballot 164 - Certificate Serial Number Entropy</b> <o:p></o:p></p>
<p>-- Motion Begins -- <o:p></o:p></p>
<p>In Section 7.1 of the Baseline Requirements, <o:p></o:p></p>
<p>REPLACE <o:p></o:p></p>
<p>"CAs SHOULD generate non-sequential Certificate serial numbers that exhibit at least 20 bits of entropy"
<o:p></o:p></p>
<p>WITH <o:p></o:p></p>
<p>"Effective April 1, 2016, CAs SHALL use a Certificate serialNumber greater than zero (0) that contains at least 64 unpredictable bits."
<o:p></o:p></p>
<p>-- Motion Ends -- <o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">_______________________________________________<br>
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