Manual:DSA dup DH(3)
DSA_dup_DH - create a DH structure out of DSA structure
#include <openssl/dsa.h> DH * DSA_dup_DH(const DSA *r);
DSA_dup_DH() duplicates DSA parameters/keys as DH parameters/keys. q is lost during that conversion, but the resulting DH parameters contain its length.
DSA_dup_DH() returns the new DH structure, and NULL on error. The error codes can be obtained by ERR_get_error(3).
Be careful to avoid small subgroup attacks when using this.
DSA_dup_DH() was added in OpenSSL 0.9.4.