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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>On the cablint report for the 20 bits of entropy, <a href="https://crt.sh/?cablint=38">https://crt.sh/?cablint=38</a>, there are 20 certificates that were listed. If this changes to 64 bits, how many more certificates will be on the list?<o:p></o:p></span></p><p class=MsoNormal><a name="_MailEndCompose"><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></a></p><span style='mso-bookmark:_MailEndCompose'></span><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><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>Ben Wilson<br><b>Sent:</b> Monday, April 18, 2016 10:25 AM<br><b>To:</b> CABFPub <public@cabforum.org><br><b>Subject:</b> [cabfpub] FW: Pre-Ballot 164 - Certificate Serial Number Entropy<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>Forwarding<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></p><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'> Kane York [<a href="mailto:kanepyork@gmail.com">mailto:kanepyork@gmail.com</a>] <br><b>Sent:</b> Monday, April 18, 2016 10:23 AM<br><b>To:</b> Ben Wilson <<a href="mailto:ben.wilson@digicert.com">ben.wilson@digicert.com</a>>; Erwann Abalea <<a href="mailto:Erwann.Abalea@docusign.com">Erwann.Abalea@docusign.com</a>><br><b>Cc:</b> <a href="mailto:questions@cabforum.org">questions@cabforum.org</a><br><b>Subject:</b> Re: [cabfpub] Pre-Ballot 164 - Certificate Serial Number Entropy<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><div><div><div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On Fri, Apr 15, 2016 at 7:52 AM Ben Wilson <<a href="mailto:ben.wilson@digicert.com">ben.wilson@digicert.com</a>> wrote:<o:p></o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-top:5.0pt;margin-right:0in;margin-bottom:5.0pt'><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>I didn’t think it was that simple. For instance, see <a href="https://en.wikipedia.org/wiki/Password_strength" target="_blank">https://en.wikipedia.org/wiki/Password_strength</a> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><a name="m_-5238551272401774583__MailEndCompose"><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> </span></a><o:p></o:p></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><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'> Erwann Abalea [mailto:<a href="mailto:Erwann.Abalea@docusign.com" target="_blank">Erwann.Abalea@docusign.com</a>] <br><b>Sent:</b> Friday, April 15, 2016 8:44 AM<br><b>To:</b> Ben Wilson <<a href="mailto:ben.wilson@digicert.com" target="_blank">ben.wilson@digicert.com</a>><br><b>Cc:</b> CABFPub <<a href="mailto:public@cabforum.org" target="_blank">public@cabforum.org</a>></span><o:p></o:p></p></div></div></div></div><div><div><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><br><b>Subject:</b> Re: [cabfpub] Pre-Ballot 164 - Certificate Serial Number Entropy</span><o:p></o:p></p></div></div></div></div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Bonjour, <o:p></o:p></p><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>20 bits of entropy is the same as 20 bits unpredictable bits.<o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Whence, 64 bits of entropy is a higher requirement than 20 bits of entropy.<o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Cordialement,<o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Erwann Abalea<o:p></o:p></p></div></div></div></div></div></blockquote><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>No, it definitely is that simple.<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I think the confusion here is the definition of "hex characters".<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>> <span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>Our CA issues certificates with 32 hexadecimal characters for the serial number.</span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><p class=MsoNormal>This is not possible - you cannot have 32 ASCII characters in the serial number.<o:p></o:p></p><div><p class=MsoNormal>The most likely truth given that explanation is that you have <b>16 fully random bytes</b>. Which would be 16 * 8 = 128 random bits, satisfying the entropy requirements.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>3 fully random bytes would satisfy the 20-bit requirement.<o:p></o:p></p></div><div><p class=MsoNormal>6 fully random hexadecimal ASCII characters encoded in the serial number would satisfy the 20-bit requirement.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>8 fully random bytes is required to satisfy the 64-bit requirement.<o:p></o:p></p></div><div><p class=MsoNormal>16 bytes with 4 bits of entropy each, which ASCII-encoded hexadecimal would be, would satisfy the entropy requirement and leave you 3.875 bytes left over for other information.<o:p></o:p></p></div></div><div><p class=MsoNormal> <o:p></o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-top:5.0pt;margin-right:0in;margin-bottom:5.0pt'><div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Le 15 avr. 2016 à 16:32, Ben Wilson <<a href="mailto:ben.wilson@digicert.com" target="_blank">ben.wilson@digicert.com</a>> a écrit :<o:p></o:p></p></div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>Forwarding</span><o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> </span><o:p></o:p></p></div><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><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'> Man Ho (Certizen) [<a href="mailto:manho@certizen.com" target="_blank"><span style='color:purple'>mailto:manho@certizen.com</span></a>] <br><b>Sent:</b> Thursday, April 14, 2016 7:51 PM<br><b>To:</b> Ben Wilson <<a href="mailto:ben.wilson@digicert.com" target="_blank"><span style='color:purple'>ben.wilson@digicert.com</span></a>>; Ryan Sleevi <<a href="mailto:sleevi@google.com" target="_blank"><span style='color:purple'>sleevi@google.com</span></a>><br><b>Cc:</b> <a href="mailto:public@cabforum.org" target="_blank"><span style='color:purple'>public@cabforum.org</span></a><br><b>Subject:</b> Re: [cabfpub] Pre-Ballot 164 - Certificate Serial Number Entropy</span><o:p></o:p></p></div></div></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'> <o:p></o:p></p></div><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt;background:white'>Ben,<br><br>We had already changed our system to issue SSL certificates with 20 hexadecimal characters of at least 20-bit of entropy since 2014. I'm just wondering why the requirement is changed from "bits of entropy" to "unpredictable bits", which I don't understand the conversion (like "cm" to "inch" :). I don't know whether our software vendor understands it.<br><br>Man<o:p></o:p></p><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'>On 4/15/2016 4:24 AM, Ben Wilson wrote:<o:p></o:p></p></div></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>You’re right, given a randomly generated 20-byte serial number, you have 159 unpredictable bits. </span><o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> </span><o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><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'> Ryan Sleevi [<a href="mailto:sleevi@google.com" target="_blank"><span style='color:purple'>mailto:sleevi@google.com</span></a>] <br><b>Sent:</b> Thursday, April 14, 2016 2:03 PM<br><b>To:</b> Ben Wilson <a href="mailto:ben.wilson@digicert.com" target="_blank"><span style='color:purple'><ben.wilson@digicert.com></span></a><br><b>Cc:</b> Man Ho (Certizen) <a href="mailto:manho@certizen.com" target="_blank"><span style='color:purple'><manho@certizen.com></span></a>; <a href="mailto:public@cabforum.org" target="_blank"><span style='color:purple'>public@cabforum.org</span></a><br><b>Subject:</b> Re: [cabfpub] Pre-Ballot 164 - Certificate Serial Number Entropy</span><o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'> <o:p></o:p></p></div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'>Ben:<o:p></o:p></p></div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'> <o:p></o:p></p></div></div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'>Are you sure your math is correct? A serial number is 20 bytes, with the high bit needing to be 1 (for the encoding of positive INTEGERS within DER). This leaves 159 bits for entropy. So you certainly can't have more unpredictable bits than that :)<o:p></o:p></p></div></div></div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'> <o:p></o:p></p></div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'>On Thu, Apr 14, 2016 at 12:59 PM, Ben Wilson <<a href="mailto:ben.wilson@digicert.com" target="_blank"><span style='color:purple'>ben.wilson@digicert.com</span></a>> wrote:<o:p></o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-top:5.0pt;margin-right:0in;margin-bottom:5.0pt'><div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>Man,</span><o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>Have you had a chance to do further research on the capabilities of your system? Our CA issues certificates with 32 hexadecimal characters for the serial number. There are 4 bits of entropy for each hexadecimal character. Therefore, our serial numbers have 128 bits of entropy and 16*32= 512 unpredictable bits. An 8-hexadecimal character serial number would have 32 bits of entropy and 128 unpredictable bits. A 20-bit entropy would be equal to 5 hexadecimal characters, or 80 unpredictable bits, so this seems like this is a downgrade to go to 64 unpredictable bits. Am I right?</span><o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>Ben</span><o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><a name="m_-5238551272401774583_m_216582708830614"><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> </span></a><o:p></o:p></p></div><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'><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'> Man Ho (Certizen) [mailto:<a href="mailto:manho@certizen.com" target="_blank"><span style='color:purple'>manho@certizen.com</span></a>] <br><b>Sent:</b> Wednesday, March 23, 2016 12:27 AM<br><b>To:</b> Ben Wilson <<a href="mailto:ben.wilson@digicert.com" target="_blank"><span style='color:purple'>ben.wilson@digicert.com</span></a>>; </span><a href="mailto:public@cabforum.org" target="_blank"><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:purple'>public@cabforum.org</span></a><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'><br><b>Subject:</b> Re: [cabfpub] Pre-Ballot 164 - Certificate Serial Number Entropy</span><o:p></o:p></p></div></div></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'> <o:p></o:p></p></div><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt;background:white'>Hi all,<br><br>Is the meaning of "at least 64 unpredictable bits" setting the same or a higher requirement than "at least 20 bits of entropy" ? I'm not quite sure whether our certificate generation software has this setting in itself.<br><br>Cheers<br>Man<o:p></o:p></p><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'>On 3/1/2016 12:21 AM, Ben Wilson wrote:<o:p></o:p></p></div></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'>REPLACE <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'>"CAs SHOULD generate non-sequential Certificate serial numbers that exhibit at least 20 bits of entropy" <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'>WITH <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'>"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></blockquote><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'> <o:p></o:p></p></div></div></div><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt;background:white'><br>_______________________________________________<br>Public mailing list<br><a href="mailto:Public@cabforum.org" target="_blank"><span style='color:purple'>Public@cabforum.org</span></a><br><a href="https://cabforum.org/mailman/listinfo/public" target="_blank"><span style='color:purple'>https://cabforum.org/mailman/listinfo/public</span></a><o:p></o:p></p></blockquote></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'> <o:p></o:p></p></div></div></blockquote><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;background:white'> <o:p></o:p></p></div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:9.0pt;font-family:"Helvetica",sans-serif;background:white'>_______________________________________________</span><span style='font-size:9.0pt;font-family:"Helvetica",sans-serif'><br><span style='background:white'>Public mailing list</span><br></span><a href="mailto:Public@cabforum.org" target="_blank"><span style='font-size:9.0pt;font-family:"Helvetica",sans-serif;color:purple;background:white'>Public@cabforum.org</span></a><span style='font-size:9.0pt;font-family:"Helvetica",sans-serif'><br></span><a href="https://cabforum.org/mailman/listinfo/public" target="_blank"><span style='font-size:9.0pt;font-family:"Helvetica",sans-serif;color:purple;background:white'>https://cabforum.org/mailman/listinfo/public</span></a><o:p></o:p></p></div></blockquote></div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div></div></div><p class=MsoNormal>_______________________________________________<br>Public mailing list<br><a href="mailto:Public@cabforum.org" target="_blank">Public@cabforum.org</a><br><a href="https://cabforum.org/mailman/listinfo/public" target="_blank">https://cabforum.org/mailman/listinfo/public</a><o:p></o:p></p></blockquote></div></div></div></div></div></div></body></html>