EVP_PKEY_GET_DEFAULT_DIGEST_NID(3)                    Library Functions Manual

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 pkey.

     Some signature algorithms, for example EVP_PKEY_ED25519, do not use a
     digest during signing.  In this case, *pnid is set to NID_undef.

     Support for the following public key algorithms is built into the
     library:

     EVP_PKEY_base_id(3)    *pnid                      return value
     EVP_PKEY_DSA           NID_sha1                   mandatory
     EVP_PKEY_EC            NID_sha1                   mandatory
     EVP_PKEY_ED25519       NID_undef                  mandatory
     EVP_PKEY_HMAC          NID_sha1                   advisory
     EVP_PKEY_RSA           NID_sha256                 advisory

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 cannot 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_asn1_set_ctrl(3), EVP_PKEY_CTX_ctrl(3), EVP_PKEY_CTX_new(3),
     EVP_PKEY_new(3), EVP_PKEY_sign(3), EVP_PKEY_verify(3),
     EVP_PKEY_verify_recover(3)

HISTORY
     EVP_PKEY_get_default_digest_nid() first appeared in OpenSSL 1.0.0 and has
     been available since OpenBSD 4.9.

Linux 6.8.2-arch2-1              March 5, 2024             Linux 6.8.2-arch2-1