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.