| 1 | =pod
|
|---|
| 2 |
|
|---|
| 3 | =head1 NAME
|
|---|
| 4 |
|
|---|
| 5 | EVP_PKEY_derive_init, EVP_PKEY_derive_set_peer, EVP_PKEY_derive - derive public key algorithm shared secret
|
|---|
| 6 |
|
|---|
| 7 | =head1 SYNOPSIS
|
|---|
| 8 |
|
|---|
| 9 | #include <openssl/evp.h>
|
|---|
| 10 |
|
|---|
| 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);
|
|---|
| 14 |
|
|---|
| 15 | =head1 DESCRIPTION
|
|---|
| 16 |
|
|---|
| 17 | The EVP_PKEY_derive_init() function initializes a public key algorithm
|
|---|
| 18 | context using key B<pkey> for shared secret derivation.
|
|---|
| 19 |
|
|---|
| 20 | The EVP_PKEY_derive_set_peer() function sets the peer key: this will normally
|
|---|
| 21 | be a public key.
|
|---|
| 22 |
|
|---|
| 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
|
|---|
| 28 | written to B<keylen>.
|
|---|
| 29 |
|
|---|
| 30 | =head1 NOTES
|
|---|
| 31 |
|
|---|
| 32 | After the call to EVP_PKEY_derive_init() algorithm specific control
|
|---|
| 33 | operations can be performed to set any appropriate parameters for the
|
|---|
| 34 | operation.
|
|---|
| 35 |
|
|---|
| 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.
|
|---|
| 38 |
|
|---|
| 39 | =head1 RETURN VALUES
|
|---|
| 40 |
|
|---|
| 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.
|
|---|
| 44 |
|
|---|
| 45 | =head1 EXAMPLES
|
|---|
| 46 |
|
|---|
| 47 | Derive shared secret (for example DH or EC keys):
|
|---|
| 48 |
|
|---|
| 49 | #include <openssl/evp.h>
|
|---|
| 50 | #include <openssl/rsa.h>
|
|---|
| 51 |
|
|---|
| 52 | EVP_PKEY_CTX *ctx;
|
|---|
| 53 | ENGINE *eng;
|
|---|
| 54 | unsigned char *skey;
|
|---|
| 55 | size_t skeylen;
|
|---|
| 56 | EVP_PKEY *pkey, *peerkey;
|
|---|
| 57 | /* NB: assumes pkey, eng, peerkey have been already set up */
|
|---|
| 58 |
|
|---|
| 59 | ctx = EVP_PKEY_CTX_new(pkey, eng);
|
|---|
| 60 | if (!ctx)
|
|---|
| 61 | /* Error occurred */
|
|---|
| 62 | if (EVP_PKEY_derive_init(ctx) <= 0)
|
|---|
| 63 | /* Error */
|
|---|
| 64 | if (EVP_PKEY_derive_set_peer(ctx, peerkey) <= 0)
|
|---|
| 65 | /* Error */
|
|---|
| 66 |
|
|---|
| 67 | /* Determine buffer length */
|
|---|
| 68 | if (EVP_PKEY_derive(ctx, NULL, &skeylen) <= 0)
|
|---|
| 69 | /* Error */
|
|---|
| 70 |
|
|---|
| 71 | skey = OPENSSL_malloc(skeylen);
|
|---|
| 72 |
|
|---|
| 73 | if (!skey)
|
|---|
| 74 | /* malloc failure */
|
|---|
| 75 |
|
|---|
| 76 | if (EVP_PKEY_derive(ctx, skey, &skeylen) <= 0)
|
|---|
| 77 | /* Error */
|
|---|
| 78 |
|
|---|
| 79 | /* Shared secret is skey bytes written to buffer skey */
|
|---|
| 80 |
|
|---|
| 81 | =head1 SEE ALSO
|
|---|
| 82 |
|
|---|
| 83 | L<EVP_PKEY_CTX_new(3)>,
|
|---|
| 84 | L<EVP_PKEY_encrypt(3)>,
|
|---|
| 85 | L<EVP_PKEY_decrypt(3)>,
|
|---|
| 86 | L<EVP_PKEY_sign(3)>,
|
|---|
| 87 | L<EVP_PKEY_verify(3)>,
|
|---|
| 88 | L<EVP_PKEY_verify_recover(3)>,
|
|---|
| 89 |
|
|---|
| 90 | =head1 HISTORY
|
|---|
| 91 |
|
|---|
| 92 | These functions were added in OpenSSL 1.0.0.
|
|---|
| 93 |
|
|---|
| 94 | =head1 COPYRIGHT
|
|---|
| 95 |
|
|---|
| 96 | Copyright 2006-2019 The OpenSSL Project Authors. All Rights Reserved.
|
|---|
| 97 |
|
|---|
| 98 | Licensed under the OpenSSL license (the "License"). You may not use
|
|---|
| 99 | this file except in compliance with the License. You can obtain a copy
|
|---|
| 100 | in the file LICENSE in the source distribution or at
|
|---|
| 101 | L<https://www.openssl.org/source/license.html>.
|
|---|
| 102 |
|
|---|
| 103 | =cut
|
|---|
