EVP_PKEY_GET_DEFAULT_DIGEST_NID(3)

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_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.