linux man page for evp_pkey_get_default_digest_nid

EVP_PKEY_get_default_digest(3SSL)                                     OpenSSL                                    EVP_PKEY_get_default_digest(3SSL)

NAME
       EVP_PKEY_get_default_digest_nid - get default signature digest

SYNOPSIS
        #include <openssl/evp.h>
        int EVP_PKEY_get_default_digest_nid(EVP_PKEY *pkey, int *pnid);

DESCRIPTION
       The EVP_PKEY_get_default_digest_nid() function sets pnid to the default message digest NID for the public key signature operations
       associated with key pkey.

NOTES
       For all current standard OpenSSL public key algorithms SHA1 is returned.

RETURN VALUES
       The EVP_PKEY_get_default_digest_nid() function returns 1 if the message digest is advisory (that is other digests can be used) and 2 if it
       is mandatory (other digests can not be used).  It returns 0 or a negative value for failure. In particular a return value of -2 indicates
       the operation is not supported by the public key algorithm.

SEE ALSO
       EVP_PKEY_CTX_new(3), EVP_PKEY_sign(3), EVP_PKEY_verify(3), EVP_PKEY_verify_recover(3),

HISTORY
       This function was first added to OpenSSL 1.0.0.

1.0.1e                                                              2013-02-11                                   EVP_PKEY_get_default_digest(3SSL)