EVP_PKEY_DERIVE(3ossl) OpenSSL EVP_PKEY_DERIVE(3ossl)
NAME
EVP_PKEY_derive_init, EVP_PKEY_derive_init_ex,
EVP_PKEY_derive_set_peer_ex, EVP_PKEY_derive_set_peer, EVP_PKEY_derive -
derive public key algorithm shared secret
SYNOPSIS
#include <openssl/evp.h>
int EVP_PKEY_derive_init(EVP_PKEY_CTX *ctx);
int EVP_PKEY_derive_init_ex(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]);
int EVP_PKEY_derive_set_peer_ex(EVP_PKEY_CTX *ctx, EVP_PKEY *peer,
int validate_peer);
int EVP_PKEY_derive_set_peer(EVP_PKEY_CTX *ctx, EVP_PKEY *peer);
int EVP_PKEY_derive(EVP_PKEY_CTX *ctx, unsigned char *key, size_t *keylen);
DESCRIPTION
EVP_PKEY_derive_init() initializes a public key algorithm context ctx for
shared secret derivation using the algorithm given when the context was
created using EVP_PKEY_CTX_new(3) or variants thereof. The algorithm is
used to fetch a EVP_KEYEXCH method implicitly, see "Implicit fetch" in
provider(7) for more information about implicit fetches.
EVP_PKEY_derive_init_ex() is the same as EVP_PKEY_derive_init() but
additionally sets the passed parameters params on the context before
returning.
EVP_PKEY_derive_set_peer_ex() sets the peer key: this will normally be a
public key. The validate_peer will validate the public key if this value
is non zero.
EVP_PKEY_derive_set_peer() is similar to EVP_PKEY_derive_set_peer_ex()
with validate_peer set to 1.
EVP_PKEY_derive(3) derives a shared secret using ctx. If key is NULL then
the maximum size of the output buffer is written to the keylen parameter.
If key is not NULL then before the call the keylen parameter should
contain the length of the key buffer, if the call is successful the
shared secret is written to key and the amount of data written to keylen.
NOTES
After the call to EVP_PKEY_derive_init(), algorithm specific control
operations can be performed to set any appropriate parameters for the
operation.
The function EVP_PKEY_derive(3) can be called more than once on the same
context if several operations are performed using the same parameters.
RETURN VALUES
EVP_PKEY_derive(3) return 1 for success and 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.
EXAMPLES
Derive shared secret (for example DH or EC keys):
#include <openssl/evp.h>
#include <openssl/rsa.h>
EVP_PKEY_CTX *ctx;
ENGINE *eng;
unsigned char *skey;
size_t skeylen;
EVP_PKEY *pkey, *peerkey;
/* NB: assumes pkey, eng, peerkey have been already set up */
ctx = EVP_PKEY_CTX_new(pkey, eng);
if (!ctx)
/* Error occurred */
if (EVP_PKEY_derive_init(ctx) <= 0)
/* Error */
if (EVP_PKEY_derive_set_peer(ctx, peerkey) <= 0)
/* Error */
/* Determine buffer length */
if (EVP_PKEY_derive(ctx, NULL, &skeylen) <= 0)
/* Error */
skey = OPENSSL_malloc(skeylen);
if (!skey)
/* malloc failure */
if (EVP_PKEY_derive(ctx, skey, &skeylen) <= 0)
/* Error */
/* Shared secret is skey bytes written to buffer skey */
SEE ALSO
EVP_PKEY_CTX_new(3), EVP_PKEY_encrypt(3), EVP_PKEY_decrypt(3),
EVP_PKEY_sign(3), EVP_PKEY_verify(3), EVP_PKEY_verify_recover(3),
EVP_KEYEXCH_fetch(3)
HISTORY
The EVP_PKEY_derive_init(), EVP_PKEY_derive_set_peer() and
EVP_PKEY_derive(3) functions were originally added in OpenSSL 1.0.0.
The EVP_PKEY_derive_init_ex() and EVP_PKEY_derive_set_peer_ex() functions
were added in OpenSSL 3.0.
COPYRIGHT
Copyright 2006-2022 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>.
3.1.0 2023-03-14 EVP_PKEY_DERIVE(3ossl)
openssl 3.1.0 - Generated Thu Mar 23 07:34:36 CDT 2023