X509_get0_distinguishing_id, X509_set0_distinguishing_id, X509_REQ_get0_distinguishing_id,

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       Licensed under the Apache License 2.0 (the "License").  You may not use this file  except  in  compliance
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       <https://www.openssl.org/source/license.html>.

3.5.0                                              2025-06-04                  X509_GET0_DISTINGUISHING_ID(3SSL)

       The Distinguishing ID is defined in FIPS 196 as follows:

       Distinguishingidentifier
           Information which unambiguously distinguishes an entity in the authentication process.

       The SM2 signature algorithm requires a Distinguishing ID value when generating and verifying a signature,
       but  the  Ddistinguishing  ID  may also find other uses.  In the context of SM2, the Distinguishing ID is
       often referred to as the "SM2 ID".

       For the purpose off verifying a certificate or a  certification  request,  a  Distinguishing  ID  may  be
       attached  to it, so functions like X509_verify(3) or X509_REQ_verify(3) have easy access to that identity
       for signature verification.

       X509_get0_distinguishing_id() gets the Distinguishing ID  value  of  a  certificate  x  by  returning  an
       ASN1_OCTET_STRING object which should not be freed by the caller.

       X509_set0_distinguishing_id()  assigns  distid to the certificate x.  Calling this function transfers the
       memory management of the value to the X509 object, and therefore the value that has been passed in should
       not be freed by the caller after this function has been called.

       X509_REQ_get0_distinguishing_id() and X509_REQ_set0_distinguishing_id() have the  same  functionality  as
       X509_get0_distinguishing_id()  and  X509_set0_distinguishing_id()  except  that  they deal with  X509_REQ
       objects instead of X509.

       X509_get0_distinguishing_id, X509_set0_distinguishing_id, X509_REQ_get0_distinguishing_id,
       X509_REQ_set0_distinguishing_id - get or set the Distinguishing ID for certificate operations

X509_set0_distinguishing_id() and X509_REQ_set0_distinguishing_id() do not return a value.

X509_verify(3), SM2(7)

        #include <openssl/x509.h>

        ASN1_OCTET_STRING *X509_get0_distinguishing_id(X509 *x);
        void X509_set0_distinguishing_id(X509 *x, ASN1_OCTET_STRING *distid);
        ASN1_OCTET_STRING *X509_REQ_get0_distinguishing_id(X509_REQ *x);
        void X509_REQ_set0_distinguishing_id(X509_REQ *x, ASN1_OCTET_STRING *distid);