#include <openssl/objects.h> ASN1_OBJECT *d2i_ASN1_OBJECT(ASN1_OBJECT **a, unsigned char **pp, long length); int i2d_ASN1_OBJECT(ASN1_OBJECT *a, unsigned char **pp);
Othewise these behave in a similar way to d2i_X509() and i2d_X509() described in the d2i_X509(3) manual page.