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 provider(7)/Implicit fetch 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 2006-2022 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.