SYNOPSIS
        #include <openssl/x509.h>

DESCRIPTION
       A X.509 certificate is a structured grouping of information about an
       individual, a device, or anything one can imagine.  A X.509 CRL
       (certificate revocation list) is a tool to help determine if a
       certificate is still valid.  The exact definition of those can be found
       in the X.509 document from ITU-T, or in RFC3280 from PKIX.  In OpenSSL,
       the type X509 is used to express such a certificate, and the type
       X509_CRL is used to express a CRL.

       A related structure is a certificate request, defined in PKCS#10 from
       RSA Security, Inc, also reflected in RFC2896.  In OpenSSL, the type
       X509_REQ is used to express such a certificate request.

       To handle some complex parts of a certificate, there are the types
       X509_NAME (to express a certificate name), X509_ATTRIBUTE (to express a
       certificate attributes), X509_EXTENSION (to express a certificate
       extension) and a few more.

       Finally, there's the supertype X509_INFO, which can contain a CRL, a
       certificate and a corresponding private key.

       X509_..., d2i_X509_... and i2d_X509_... handle X.509 certificates, with
       some exceptions, shown below.

       X509_CRL_..., d2i_X509_CRL_... and i2d_X509_CRL_...  handle X.509 CRLs.

       X509_REQ_..., d2i_X509_REQ_... and i2d_X509_REQ_...  handle PKCS#10
       certificate requests.

       X509_NAME_... handle certificate names.

       X509_ATTRIBUTE_... handle certificate attributes.

       X509_EXTENSION_... handle certificate extensions.

SEE ALSO
       x509_name_entry_get_object(3), x509_name_add_entry_by_txt(3),
       x509_name_add_entry_by_nid(3), x509_name_print_ex(3), x509_name_new(3),
       d2i_x509(3), d2i_x509_algor(3), d2i_x509_crl(3), d2i_x509_name(3),
       d2i_x509_req(3), d2i_x509_sig(3), crypto(3), x509v3(3)