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.
DH_new(3), DSA_new(3), ERR_get_error(3)
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