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
#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);
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() 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.
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() can be called more than once on the same
context if several operations are performed using the same parameters.
EVP_PKEY_derive_init() and
EVP_PKEY_derive() 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.
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 */
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)
The
EVP_PKEY_derive_init(),
EVP_PKEY_derive_set_peer() and
EVP_PKEY_derive() 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 2006-2023 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>.