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--></style></head><body lang=EN-US link=blue vlink=purple style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal><span style='font-size:12.0pt'>“OPTIONAL” means the parser <u>must</u> deal with complete absence, not only encoded as ASN.1 NULL.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt'>Broken parsers should be fixed.<o:p></o:p></span></p><div><div><p class=MsoNormal><span style='color:black'>--<o:p></o:p></span></p><p class=MsoNormal><span style='color:black'>Regards,<o:p></o:p></span></p><p class=MsoNormal><span style='color:black'>Uri<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><i><o:p> </o:p></i></p><p class=MsoNormal><i><span style='color:black'>There are two ways to design a system. One is to make is so simple there are obviously no deficiencies.</span></i><span style='font-size:12.0pt;color:black'><o:p></o:p></span></p><p class=MsoNormal><i><span style='color:black'>The other is to make it so complex there are no obvious deficiencies.</span></i><span style='font-size:12.0pt;color:black'><o:p></o:p></span></p><p class=MsoNormal><i><span style='color:black'> - C. A. R. Hoare</span></i><span style='font-size:12.0pt;color:black'><o:p></o:p></span></p></div></div><p class=MsoNormal><span style='font-size:12.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt'><o:p> </o:p></span></p><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='margin-left:.5in'><b><span style='font-size:12.0pt;color:black'>From: </span></b><span style='font-size:12.0pt;color:black'>openssl-users-bounce <openssl-users-bounces@openssl.org> on behalf of openssl-users <openssl-users@openssl.org><br><b>Organization: </b>WiseMo A/S<br><b>Reply-To: </b>Jakob Bohm <jb-openssl@wisemo.com><br><b>Date: </b>Thursday, January 28, 2021 at 21:10<br><b>To: </b>openssl-users <openssl-users@openssl.org><br><b>Subject: </b>Re: Encoding of AlgorithmIdentifier with NULL parameters<o:p></o:p></span></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:12.0pt;margin-left:.5in'><tt><span style='font-size:10.0pt'>Also note that the official ASN.1 declaration for </span></tt><span style='font-size:10.0pt;font-family:"Courier New"'><br><tt>AlgorithmIdentifier (from X.509 (2012), section 7.2) marks </tt><br><tt>the parameters field as OPTIONAL, so parsers really should </tt><br><tt>accept its absence.</tt><br><br><tt>However if broken parsers are common (this thread </tt><br><tt>only found one such parser), maybe it would be </tt><br><tt>good practice to include the NULL value for compatibility.</tt><br><br><tt>AlgorithmIdentifier{ALGORITHM:SupportedAlgorithms} ::= SEQUENCE {</tt><br><tt> algorithm ALGORITHM.&id({SupportedAlgorithms}),</tt><br><tt> parameters ALGORITHM.&Type({SupportedAlgorithms}{@algorithm}) OPTIONAL,</tt><br><tt>... }</tt></span><o:p></o:p></p></div></body></html>