5 EVP_PKEY_derive_init, EVP_PKEY_derive_set_peer, EVP_PKEY_derive - derive public key algorithm shared secret
9 #include <openssl/evp.h>
11 int EVP_PKEY_derive_init(EVP_PKEY_CTX *ctx);
12 int EVP_PKEY_derive_set_peer(EVP_PKEY_CTX *ctx, EVP_PKEY *peer);
13 int EVP_PKEY_derive(EVP_PKEY_CTX *ctx, unsigned char *key, size_t *keylen);
17 The EVP_PKEY_derive_init() function initializes a public key algorithm
18 context using key B<pkey> for shared secret derivation.
20 The EVP_PKEY_derive_set_peer() function sets the peer key: this will normally
23 The EVP_PKEY_derive() derives a shared secret using B<ctx>.
24 If B<key> is B<NULL> then the maximum size of the output buffer is written to
25 the B<keylen> parameter. If B<key> is not B<NULL> then before the call the
26 B<keylen> parameter should contain the length of the B<key> buffer, if the call
27 is successful the shared secret is written to B<key> and the amount of data
32 After the call to EVP_PKEY_derive_init() algorithm specific control
33 operations can be performed to set any appropriate parameters for the
36 The function EVP_PKEY_derive() can be called more than once on the same
37 context if several operations are performed using the same parameters.
41 EVP_PKEY_derive_init() and EVP_PKEY_derive() return 1 for success and 0
42 or a negative value for failure. In particular a return value of -2
43 indicates the operation is not supported by the public key algorithm.
47 Derive shared secret (for example DH or EC keys):
49 #include <openssl/evp.h>
50 #include <openssl/rsa.h>
55 EVP_PKEY *pkey, *peerkey;
56 /* NB: assumes pkey, peerkey have been already set up */
58 ctx = EVP_PKEY_CTX_new(pkey);
61 if (EVP_PKEY_derive_init(ctx) <= 0)
63 if (EVP_PKEY_derive_set_peer(ctx, peerkey) <= 0)
66 /* Determine buffer length */
67 if (EVP_PKEY_derive(ctx, NULL, &skeylen) <= 0)
70 skey = OPENSSL_malloc(skeylen);
75 if (EVP_PKEY_derive(ctx, skey, &skeylen) <= 0)
78 /* Shared secret is skey bytes written to buffer skey */
82 L<EVP_PKEY_CTX_new(3)>,
83 L<EVP_PKEY_encrypt(3)>,
84 L<EVP_PKEY_decrypt(3)>,
86 L<EVP_PKEY_verify(3)>,
87 L<EVP_PKEY_verify_recover(3)>,
91 These functions were first added to OpenSSL 1.0.0.
95 Copyright 2006-2016 The OpenSSL Project Authors. All Rights Reserved.
97 Licensed under the OpenSSL license (the "License"). You may not use
98 this file except in compliance with the License. You can obtain a copy
99 in the file LICENSE in the source distribution or at
100 L<https://www.openssl.org/source/license.html>.