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This type was previously described in a note, which is hard to find unless you already know where to look. This change makes the description more prominent, and allows indexing by adding it in the NAMES section. The EVP_PKEY description is altered to conceptually allow an EVP_PKEY to contain a private key without a corresponding public key. This is related to an OTC vote: https://mta.openssl.org/pipermail/openssl-project/2020-December/002474.html The description of EVP_PKEY for MAC purposes is amended to fit. Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com> (Merged from https://github.com/openssl/openssl/pull/13629)
216 lines
9.9 KiB
Plaintext
216 lines
9.9 KiB
Plaintext
=pod
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=head1 NAME
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EVP_PKEY,
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EVP_PKEY_new,
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EVP_PKEY_up_ref,
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EVP_PKEY_free,
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EVP_PKEY_new_raw_private_key_ex,
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EVP_PKEY_new_raw_private_key,
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EVP_PKEY_new_raw_public_key_ex,
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EVP_PKEY_new_raw_public_key,
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EVP_PKEY_new_CMAC_key_ex,
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EVP_PKEY_new_CMAC_key,
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EVP_PKEY_new_mac_key,
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EVP_PKEY_get_raw_private_key,
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EVP_PKEY_get_raw_public_key
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- public/private key allocation and raw key handling functions
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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typedef evp_pkey_st EVP_PKEY;
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EVP_PKEY *EVP_PKEY_new(void);
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int EVP_PKEY_up_ref(EVP_PKEY *key);
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void EVP_PKEY_free(EVP_PKEY *key);
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EVP_PKEY *EVP_PKEY_new_raw_private_key_ex(OSSL_LIB_CTX *libctx,
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const char *keytype,
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const char *propq,
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const unsigned char *key,
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size_t keylen);
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EVP_PKEY *EVP_PKEY_new_raw_private_key(int type, ENGINE *e,
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const unsigned char *key, size_t keylen);
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EVP_PKEY *EVP_PKEY_new_raw_public_key_ex(OSSL_LIB_CTX *libctx,
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const char *keytype,
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const char *propq,
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const unsigned char *key,
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size_t keylen);
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EVP_PKEY *EVP_PKEY_new_raw_public_key(int type, ENGINE *e,
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const unsigned char *key, size_t keylen);
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EVP_PKEY *EVP_PKEY_new_CMAC_key_ex(const unsigned char *priv, size_t len,
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const char *cipher_name,
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OSSL_LIB_CTX *libctx, const char *propq);
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EVP_PKEY *EVP_PKEY_new_CMAC_key(ENGINE *e, const unsigned char *priv,
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size_t len, const EVP_CIPHER *cipher);
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EVP_PKEY *EVP_PKEY_new_mac_key(int type, ENGINE *e, const unsigned char *key,
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int keylen);
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int EVP_PKEY_get_raw_private_key(const EVP_PKEY *pkey, unsigned char *priv,
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size_t *len);
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int EVP_PKEY_get_raw_public_key(const EVP_PKEY *pkey, unsigned char *pub,
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size_t *len);
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=head1 DESCRIPTION
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B<EVP_PKEY> is a generic structure to hold diverse types of asymmetric keys
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(also known as "key pairs"), and can be used for diverse operations, like
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signing, verifying signatures, key derivation, etc. The asymmetric keys
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themselves are often refered to as the "internal key", and are handled by
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backends, such as providers (through L<EVP_KEYMGMT(3)>) or B<ENGINE>s.
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Conceptually, an B<EVP_PKEY> internal key may hold a private key, a public
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key, or both (a keypair), and along with those, key parameters if the key type
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requires them. The presence of these components determine what operations can
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be made; for example, signing normally requires the presence of a private key,
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and verifying normally requires the presence of a public key.
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=for comment ED signature require both the private and public key...
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B<EVP_PKEY> has also been used for MAC algorithm that were conceived as
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producing signatures, although not being public key algorithms; "POLY1305",
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"SIPHASH", "HMAC", "CMAC". This usage is considered legacy and is discouraged
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in favor of the L<EVP_MAC(3)> API.
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The EVP_PKEY_new() function allocates an empty B<EVP_PKEY> structure which is
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used by OpenSSL to store public and private keys. The reference count is set to
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B<1>.
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EVP_PKEY_up_ref() increments the reference count of I<key>.
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EVP_PKEY_free() decrements the reference count of I<key> and, if the reference
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count is zero, frees it up. If I<key> is NULL, nothing is done.
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EVP_PKEY_new_raw_private_key_ex() allocates a new B<EVP_PKEY>. Unless an
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engine should be used for the key type, a provider for the key is found using
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the library context I<libctx> and the property query string I<propq>. The
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I<keytype> argument indicates what kind of key this is. The value should be a
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string for a public key algorithm that supports raw private keys, i.e one of
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"X25519", "ED25519", "X448" or "ED448". I<key> points to the raw private key
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data for this B<EVP_PKEY> which should be of length I<keylen>. The length
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should be appropriate for the type of the key. The public key data will be
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automatically derived from the given private key data (if appropriate for the
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algorithm type).
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EVP_PKEY_new_raw_private_key() does the same as
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EVP_PKEY_new_raw_private_key_ex() except that the default library context and
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default property query are used instead. If I<e> is non-NULL then the new
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B<EVP_PKEY> structure is associated with the engine I<e>. The I<type> argument
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indicates what kind of key this is. The value should be a NID for a public key
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algorithm that supports raw private keys, i.e. one of B<EVP_PKEY_X25519>,
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B<EVP_PKEY_ED25519>, B<EVP_PKEY_X448> or B<EVP_PKEY_ED448>.
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EVP_PKEY_new_raw_private_key_ex() and EVP_PKEY_new_raw_private_key() may also
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be used with most MACs implemented as public key algorithms, so key types such
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as "HMAC", "POLY1305", "SIPHASH", or their NID form B<EVP_PKEY_POLY1305>,
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B<EVP_PKEY_SIPHASH>, B<EVP_PKEY_HMAC> are also accepted. This usage is,
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as mentioned above, discouraged in favor of the L<EVP_MAC(3)> API.
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EVP_PKEY_new_raw_public_key_ex() works in the same way as
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EVP_PKEY_new_raw_private_key_ex() except that I<key> points to the raw
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public key data. The B<EVP_PKEY> structure will be initialised without any
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private key information. Algorithm types that support raw public keys are
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"X25519", "ED25519", "X448" or "ED448".
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EVP_PKEY_new_raw_public_key() works in the same way as
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EVP_PKEY_new_raw_private_key() except that I<key> points to the raw public key
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data. The B<EVP_PKEY> structure will be initialised without any private key
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information. Algorithm types that support raw public keys are
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B<EVP_PKEY_X25519>, B<EVP_PKEY_ED25519>, B<EVP_PKEY_X448> or B<EVP_PKEY_ED448>.
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EVP_PKEY_new_CMAC_key_ex() works in the same way as
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EVP_PKEY_new_raw_private_key() except it is only for the B<EVP_PKEY_CMAC>
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algorithm type. In addition to the raw private key data, it also takes a cipher
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algorithm to be used during creation of a CMAC in the I<cipher> argument. The
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cipher should be a standard encryption only cipher. For example AEAD and XTS
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ciphers should not be used. Finally it also takes a library context I<libctx>
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and property query I<propq> which are used when fetching any cryptographic
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algorithms which may be NULL to use the default values.
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EVP_PKEY_new_CMAC_key() is the same as EVP_PKEY_new_CMAC_key_ex()
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except that the default values are used for I<libctx> and I<propq>.
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Using EVP_PKEY_new_CMAC_key_ex() or EVP_PKEY_new_CMAC_key() is discouraged in
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favor of the L<EVP_MAC(3)> API.
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EVP_PKEY_new_mac_key() works in the same way as EVP_PKEY_new_raw_private_key().
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New applications should use EVP_PKEY_new_raw_private_key() instead.
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EVP_PKEY_get_raw_private_key() fills the buffer provided by I<priv> with raw
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private key data. The size of the I<priv> buffer should be in I<*len> on entry
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to the function, and on exit I<*len> is updated with the number of bytes
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actually written. If the buffer I<priv> is NULL then I<*len> is populated with
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the number of bytes required to hold the key. The calling application is
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responsible for ensuring that the buffer is large enough to receive the private
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key data. This function only works for algorithms that support raw private keys.
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Currently this is: B<EVP_PKEY_HMAC>, B<EVP_PKEY_POLY1305>, B<EVP_PKEY_SIPHASH>,
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B<EVP_PKEY_X25519>, B<EVP_PKEY_ED25519>, B<EVP_PKEY_X448> or B<EVP_PKEY_ED448>.
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EVP_PKEY_get_raw_public_key() fills the buffer provided by I<pub> with raw
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public key data. The size of the I<pub> buffer should be in I<*len> on entry
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to the function, and on exit I<*len> is updated with the number of bytes
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actually written. If the buffer I<pub> is NULL then I<*len> is populated with
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the number of bytes required to hold the key. The calling application is
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responsible for ensuring that the buffer is large enough to receive the public
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key data. This function only works for algorithms that support raw public keys.
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Currently this is: B<EVP_PKEY_X25519>, B<EVP_PKEY_ED25519>, B<EVP_PKEY_X448> or
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B<EVP_PKEY_ED448>.
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=head1 NOTES
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The B<EVP_PKEY> structure is used by various OpenSSL functions which require a
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general private key without reference to any particular algorithm.
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The structure returned by EVP_PKEY_new() is empty. To add a private or public
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key to this empty structure use the appropriate functions described in
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L<EVP_PKEY_set1_RSA(3)>, L<EVP_PKEY_set1_DSA(3)>, L<EVP_PKEY_set1_DH(3)> or
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L<EVP_PKEY_set1_EC_KEY(3)>.
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=head1 RETURN VALUES
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EVP_PKEY_new(), EVP_PKEY_new_raw_private_key(), EVP_PKEY_new_raw_public_key(),
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EVP_PKEY_new_CMAC_key() and EVP_PKEY_new_mac_key() return either the newly
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allocated B<EVP_PKEY> structure or B<NULL> if an error occurred.
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EVP_PKEY_up_ref(), EVP_PKEY_get_raw_private_key() and
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EVP_PKEY_get_raw_public_key() return 1 for success and 0 for failure.
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=head1 SEE ALSO
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L<EVP_PKEY_set1_RSA(3)>, L<EVP_PKEY_set1_DSA(3)>, L<EVP_PKEY_set1_DH(3)> or
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L<EVP_PKEY_set1_EC_KEY(3)>
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=head1 HISTORY
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The
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EVP_PKEY_new() and EVP_PKEY_free() functions exist in all versions of OpenSSL.
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The EVP_PKEY_up_ref() function was added in OpenSSL 1.1.0.
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The
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EVP_PKEY_new_raw_private_key(), EVP_PKEY_new_raw_public_key(),
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EVP_PKEY_new_CMAC_key(), EVP_PKEY_new_raw_private_key() and
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EVP_PKEY_get_raw_public_key() functions were added in OpenSSL 1.1.1.
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The EVP_PKEY_new_raw_private_key_ex(),
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EVP_PKEY_new_raw_public_key_ex() and
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EVP_PKEY_new_CMAC_key_ex() functions were added in OpenSSL 3.0.
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The documentation of B<EVP_PKEY> was amended in OpenSSL 3.0 to allow there to
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be the private part of the keypair without the public part, where this was
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previously implied to be disallowed.
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=head1 COPYRIGHT
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Copyright 2002-2020 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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