NAME

       EVP_PKEY, EVP_PKEY_new, EVP_PKEY_up_ref, EVP_PKEY_dup, EVP_PKEY_free, EVP_PKEY_new_raw_private_key_ex,
       EVP_PKEY_new_raw_private_key, EVP_PKEY_new_raw_public_key_ex, EVP_PKEY_new_raw_public_key,
       EVP_PKEY_new_CMAC_key, EVP_PKEY_new_mac_key, EVP_PKEY_get_raw_private_key, EVP_PKEY_get_raw_public_key -
       public/private key allocation and raw key handling functions

SYNOPSIS

        #include <openssl/evp.h>

        typedef evp_pkey_st EVP_PKEY;

        EVP_PKEY *EVP_PKEY_new(void);
        int EVP_PKEY_up_ref(EVP_PKEY *key);
        EVP_PKEY *EVP_PKEY_dup(EVP_PKEY *key);
        void EVP_PKEY_free(EVP_PKEY *key);

        EVP_PKEY *EVP_PKEY_new_raw_private_key_ex(OSSL_LIB_CTX *libctx,
                                                  const char *keytype,
                                                  const char *propq,
                                                  const unsigned char *key,
                                                  size_t keylen);
        EVP_PKEY *EVP_PKEY_new_raw_private_key(int type, ENGINE *e,
                                               const unsigned char *key, size_t keylen);
        EVP_PKEY *EVP_PKEY_new_raw_public_key_ex(OSSL_LIB_CTX *libctx,
                                                 const char *keytype,
                                                 const char *propq,
                                                 const unsigned char *key,
                                                 size_t keylen);
        EVP_PKEY *EVP_PKEY_new_raw_public_key(int type, ENGINE *e,
                                              const unsigned char *key, size_t keylen);
        EVP_PKEY *EVP_PKEY_new_mac_key(int type, ENGINE *e, const unsigned char *key,
                                       int keylen);

        int EVP_PKEY_get_raw_private_key(const EVP_PKEY *pkey, unsigned char *priv,
                                         size_t *len);
        int EVP_PKEY_get_raw_public_key(const EVP_PKEY *pkey, unsigned char *pub,
                                        size_t *len);

       The following function has been deprecated since OpenSSL 3.0, and can be hidden entirely by defining
       OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

        EVP_PKEY *EVP_PKEY_new_CMAC_key(ENGINE *e, const unsigned char *priv,
                                        size_t len, const EVP_CIPHER *cipher);

DESCRIPTION

       EVP_PKEY is a generic structure to hold diverse types of asymmetric keys (also known as "key pairs"), and
       can be used for diverse operations, like signing, verifying signatures, key derivation, etc.  The
       asymmetric keys themselves are often referred to as the "internal key", and are handled by backends, such
       as providers (through EVP_KEYMGMT(3)) or ENGINEs.

       Conceptually, an EVP_PKEY internal key may hold a private key, a public key, or both (a keypair), and
       along with those, key parameters if the key type requires them.  The presence of these components
       determine what operations can be made; for example, signing normally requires the presence of a private
       key, and verifying normally requires the presence of a public key.

       EVP_PKEY has also been used for MAC algorithm that were conceived as producing signatures, although not
       being public key algorithms; "POLY1305", "SIPHASH", "HMAC", "CMAC".  This usage is considered legacy and
       is discouraged in favor of the EVP_MAC(3) API.

       The EVP_PKEY_new() function allocates an empty EVP_PKEY structure which is used by OpenSSL to store
       public and private keys. The reference count is set to 1.

       EVP_PKEY_up_ref() increments the reference count of key.

       EVP_PKEY_dup() duplicates the key. The key must not be ENGINE based or a raw key, otherwise the
       duplication will fail.

       EVP_PKEY_free() decrements the reference count of key and, if the reference count is zero, frees it up.
       If key is NULL, nothing is done.

       EVP_PKEY_new_raw_private_key_ex() allocates a new EVP_PKEY. Unless an engine should be used for the key
       type, a provider for the key is found using the library context libctx and the property query string
       propq. The keytype argument indicates what kind of key this is. The value should be a string for a public
       key algorithm that supports raw private keys, i.e one of "X25519", "ED25519", "X448" or "ED448". key
       points to the raw private key data for this EVP_PKEY which should be of length keylen. The length should
       be appropriate for the type of the key. The public key data will be automatically derived from the given
       private key data (if appropriate for the algorithm type).

       EVP_PKEY_new_raw_private_key() does the same as EVP_PKEY_new_raw_private_key_ex() except that the default
       library context and default property query are used instead. If e is non-NULL then the new EVP_PKEY
       structure is associated with the engine e. The type argument indicates what kind of key this is. The
       value should be a NID for a public key algorithm that supports raw private keys, i.e. one of
       EVP_PKEY_X25519, EVP_PKEY_ED25519, EVP_PKEY_X448 or EVP_PKEY_ED448.

       EVP_PKEY_new_raw_private_key_ex() and EVP_PKEY_new_raw_private_key() may also be used with most MACs
       implemented as public key algorithms, so key types such as "HMAC", "POLY1305", "SIPHASH", or their NID
       form EVP_PKEY_POLY1305, EVP_PKEY_SIPHASH, EVP_PKEY_HMAC are also accepted.  This usage is, as mentioned
       above, discouraged in favor of the EVP_MAC(3) API.

       EVP_PKEY_new_raw_public_key_ex() works in the same way as EVP_PKEY_new_raw_private_key_ex() except that
       key points to the raw public key data. The EVP_PKEY structure will be initialised without any private key
       information. Algorithm types that support raw public keys are "X25519", "ED25519", "X448" or "ED448".

       EVP_PKEY_new_raw_public_key() works in the same way as EVP_PKEY_new_raw_private_key() except that key
       points to the raw public key data. The EVP_PKEY structure will be initialised without any private key
       information. Algorithm types that support raw public keys are EVP_PKEY_X25519, EVP_PKEY_ED25519,
       EVP_PKEY_X448 or EVP_PKEY_ED448.

       EVP_PKEY_new_mac_key() works in the same way as EVP_PKEY_new_raw_private_key().  New applications should
       use EVP_PKEY_new_raw_private_key() instead.

       EVP_PKEY_get_raw_private_key() fills the buffer provided by priv with raw private key data. The size of
       the priv buffer should be in *len on entry to the function, and on exit *len is updated with the number
       of bytes actually written. If the buffer priv is NULL then *len is populated with the number of bytes
       required to hold the key. The calling application is responsible for ensuring that the buffer is large
       enough to receive the private key data. This function only works for algorithms that support raw private
       keys.  Currently this is: EVP_PKEY_HMAC, EVP_PKEY_POLY1305, EVP_PKEY_SIPHASH, EVP_PKEY_X25519,
       EVP_PKEY_ED25519, EVP_PKEY_X448 or EVP_PKEY_ED448.

       EVP_PKEY_get_raw_public_key() fills the buffer provided by pub with raw public key data. The size of the
       pub buffer should be in *len on entry to the function, and on exit *len is updated with the number of
       bytes actually written. If the buffer pub is NULL then *len is populated with the number of bytes
       required to hold the key. The calling application is responsible for ensuring that the buffer is large
       enough to receive the public key data. This function only works for algorithms that support raw public
       keys.  Currently this is: EVP_PKEY_X25519, EVP_PKEY_ED25519, EVP_PKEY_X448 or EVP_PKEY_ED448.

       EVP_PKEY_new_CMAC_key() works in the same way as EVP_PKEY_new_raw_private_key() except it is only for the
       EVP_PKEY_CMAC algorithm type. In addition to the raw private key data, it also takes a cipher algorithm
       to be used during creation of a CMAC in the cipher argument. The cipher should be a standard encryption-
       only cipher. For example AEAD and XTS ciphers should not be used.

       Applications should use the EVP_MAC(3) API instead and set the OSSL_MAC_PARAM_CIPHER parameter on the
       EVP_MAC_CTX object with the name of the cipher being used.

NOTES

       The EVP_PKEY structure is used by various OpenSSL functions which require a general private key without
       reference to any particular algorithm.

       The structure returned by EVP_PKEY_new() is empty. To add a private or public key to this empty structure
       use the appropriate functions described in EVP_PKEY_set1_RSA(3), EVP_PKEY_set1_DSA(3),
       EVP_PKEY_set1_DH(3) or EVP_PKEY_set1_EC_KEY(3).

RETURN VALUES

       EVP_PKEY_new(), EVP_PKEY_new_raw_private_key(), EVP_PKEY_new_raw_public_key(), EVP_PKEY_new_CMAC_key()
       and EVP_PKEY_new_mac_key() return either the newly allocated EVP_PKEY structure or NULL if an error
       occurred.

       EVP_PKEY_dup() returns the key duplicate or NULL if an error occurred.

       EVP_PKEY_up_ref(), EVP_PKEY_get_raw_private_key() and EVP_PKEY_get_raw_public_key() return 1 for success
       and 0 for failure.

SEE ALSO

       EVP_PKEY_set1_RSA(3), EVP_PKEY_set1_DSA(3), EVP_PKEY_set1_DH(3) or EVP_PKEY_set1_EC_KEY(3)

HISTORY

       The EVP_PKEY_new() and EVP_PKEY_free() functions exist in all versions of OpenSSL.

       The EVP_PKEY_up_ref() function was added in OpenSSL 1.1.0.

       The EVP_PKEY_new_raw_private_key(), EVP_PKEY_new_raw_public_key(), EVP_PKEY_new_CMAC_key(),
       EVP_PKEY_new_raw_private_key() and EVP_PKEY_get_raw_public_key() functions were added in OpenSSL 1.1.1.

       The EVP_PKEY_dup(), EVP_PKEY_new_raw_private_key_ex(), and EVP_PKEY_new_raw_public_key_ex() functions
       were added in OpenSSL 3.0.

       The EVP_PKEY_new_CMAC_key() was deprecated in OpenSSL 3.0.

       The documentation of EVP_PKEY was amended in OpenSSL 3.0 to allow there to be the private part of the
       keypair without the public part, where this was previously implied to be disallowed.

COPYRIGHT

       Copyright 2002-2023 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>.