NAME

       EVP_PKEY_get_default_digest_nid, EVP_PKEY_get_default_digest_name - get default signature
       digest

SYNOPSIS

        #include <openssl/evp.h>

        int EVP_PKEY_get_default_digest_name(EVP_PKEY *pkey,
                                             char *mdname, size_t mdname_sz);
        int EVP_PKEY_get_default_digest_nid(EVP_PKEY *pkey, int *pnid);

DESCRIPTION

       EVP_PKEY_get_default_digest_name() fills in the default message digest name for the public
       key signature operations associated with key pkey into mdname, up to at most mdname_sz
       bytes including the ending NUL byte.  The name could be "UNDEF", signifying that no digest
       should be used.

       EVP_PKEY_get_default_digest_nid() sets pnid to the default message digest NID for the
       public key signature operations associated with key pkey.  Note that some signature
       algorithms (i.e. Ed25519 and Ed448) do not use a digest during signing.  In this case pnid
       will be set to NID_undef.  This function is only reliable for legacy keys, which are keys
       with a EVP_PKEY_ASN1_METHOD; these keys have typically been loaded from engines, or
       created with EVP_PKEY_assign_RSA(3) or similar.

NOTES

       For all current standard OpenSSL public key algorithms SHA256 is returned.

RETURN VALUES

       EVP_PKEY_get_default_digest_name() and EVP_PKEY_get_default_digest_nid() both return 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).  They return 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_digestsign_supports_digest(3),
       EVP_PKEY_verify(3), EVP_PKEY_verify_recover(3),

HISTORY

       This function was added in OpenSSL 1.0.0.

COPYRIGHT

       Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file except
       in compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.