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 dependent 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_new_method() allocates and initializes a DSA structure so that engine will be used for the DSA operations. If engine is NULL, the default engine for DSA operations is used, and if no default ENGINE is set, the DSA_METHOD controlled by DSA_set_default_method() is used.