text: DSA_set_default_method, DSA_get_default_method, DSA_set_method, DSA_new_method, DSA_OpenSSL - select DSA method
  #include <openssl/dsa.h> #include <openssl/engine.h>
  void DSA_set_default_method(const DSA_METHOD *meth);
  const DSA_METHOD *DSA_get_default_method(void);
  int DSA_set_method(DSA *dsa, const DSA_METHOD *meth);
  DSA *DSA_new_method(ENGINE *engine);
  DSA_METHOD *DSA_OpenSSL(void);
  A DSA_METHOD specifies the functions that OpenSSL uses for DSA operations. By modifying the method, alternative implementations such as hardware accelerators may be used. IMPORTANT: See the NOTES section for important information about how these DSA API functions are affected by the use of ENGINE API calls.
  Initially, the default DSA_METHOD is the OpenSSL internal implementation, as returned by DSA_OpenSSL().
  DSA_set_default_method() makes meth the default method for all DSA structures created later. NB: This is true only whilst no ENGINE has been set as a default for DSA, so this function is no longer recommended.
  DSA_get_default_method() returns a pointer to the current default DSA_METHOD. However, the meaningfulness of this result is dependant on whether the ENGINE API is being used, so this function is no longer recommended.
  DSA_set_method() selects meth to perform all operations using the key rsa. This will replace the DSA_METHOD used by the DSA key and if the previous method was supplied by an ENGINE, the handle to that ENGINE will be released during the change. It is possible to have DSA keys that only work with certain DSA_METHOD implementations (eg. from an ENGINE module that supports embedded hardware-protected keys), and in such cases attempting to change the DSA_METHOD for the key can have unexpected results..
  DSA_set_method() returns non-zero if the provided meth was successfully set as the method for dsa (including unloading the ENGINE handle if the previous method was supplied by an ENGINE).
  DSA_new_method() returns NULL and sets an error code that can be obtained by ERR_get_error(3) if the allocation fails. Otherwise it returns a pointer to the newly allocated structure..