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<title>GnuTLS 3.4.8: X.509 certificate structure</title>
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<a name="X_002e509-certificate-structure"></a>
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<p>
Next: <a href="Importing-an-X_002e509-certificate.html#Importing-an-X_002e509-certificate" accesskey="n" rel="next">Importing an X.509 certificate</a>, Up: <a href="X_002e509-certificates.html#X_002e509-certificates" accesskey="u" rel="up">X.509 certificates</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="X_002e509-certificate-structure-1"></a>
<h4 class="subsubsection">4.1.1.1 <acronym>X.509</acronym> certificate structure</h4>
<p>An <acronym>X.509</acronym> certificate usually contains information about the
certificate holder, the signer, a unique serial number, expiration
dates and some other fields [<em>PKIX</em>] as shown in <a href="#tab_003ax509">Table 4.2</a>.
</p>
<div class="float"><a name="tab_003ax509"></a>
<table>
<thead><tr><th width="20%">Field</th><th width="70%">Description</th></tr></thead>
<tr><td width="20%">version</td><td width="70%">The field that indicates the version of the certificate.</td></tr>
<tr><td width="20%">serialNumber</td><td width="70%">This field holds a unique serial number per certificate.</td></tr>
<tr><td width="20%">signature</td><td width="70%">The issuing authority’s signature.</td></tr>
<tr><td width="20%">issuer</td><td width="70%">Holds the issuer’s distinguished name.</td></tr>
<tr><td width="20%">validity</td><td width="70%">The activation and expiration dates.</td></tr>
<tr><td width="20%">subject</td><td width="70%">The subject’s distinguished name of the certificate.</td></tr>
<tr><td width="20%">extensions</td><td width="70%">The extensions are fields only present in version 3 certificates.</td></tr>
</table>
<div class="float-caption"><p><strong>Table 4.2: </strong>X.509 certificate fields.</p></div></div>
<p>The certificate’s <em>subject or issuer name</em> is not just a single
string. It is a Distinguished name and in the <acronym>ASN.1</acronym>
notation is a sequence of several object identifiers with their corresponding
values. Some of available OIDs to be used in an <acronym>X.509</acronym>
distinguished name are defined in <samp>gnutls/x509.h</samp>.
</p>
<p>The <em>Version</em> field in a certificate has values either 1 or 3 for
version 3 certificates. Version 1 certificates do not support the
extensions field so it is not possible to distinguish a CA from a
person, thus their usage should be avoided.
</p>
<p>The <em>validity</em> dates are there to indicate the date that the
specific certificate was activated and the date the certificate’s key
would be considered invalid.
</p>
<p>In <acronym>GnuTLS</acronym> the <acronym>X.509</acronym> certificate structures are
handled using the <code>gnutls_x509_crt_t</code> type and the corresponding
private keys with the <code>gnutls_x509_privkey_t</code> type. All the
available functions for <acronym>X.509</acronym> certificate handling have
their prototypes in <samp>gnutls/x509.h</samp>. An example program to
demonstrate the <acronym>X.509</acronym> parsing capabilities can be found in
<a href="X_002e509-certificate-parsing-example.html#ex_002dx509_002dinfo">ex-x509-info</a>.
</p>
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Next: <a href="Importing-an-X_002e509-certificate.html#Importing-an-X_002e509-certificate" accesskey="n" rel="next">Importing an X.509 certificate</a>, Up: <a href="X_002e509-certificates.html#X_002e509-certificates" accesskey="u" rel="up">X.509 certificates</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
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