bionic (3) EVP_PKEY_derive_init.3ssl.gz

Provided by: libssl-doc_1.1.1-1ubuntu2.1~18.04.23_all bug

NAME
       EVP_PKEY_derive_init, 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_set_peer(EVP_PKEY_CTX *ctx, EVP_PKEY *peer);
        int EVP_PKEY_derive(EVP_PKEY_CTX *ctx, unsigned char *key, size_t *keylen);


DESCRIPTION
       The EVP_PKEY_derive_init() function initializes a public key algorithm context using key pkey for shared
       secret derivation.

       The EVP_PKEY_derive_set_peer() function sets the peer key: this will normally be a public key.

       The 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.


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() can be called more than once on the same context if several operations are
       performed using the same parameters.


RETURN VALUES
       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.


EXAMPLE
       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),


HISTORY
       These functions were first added to OpenSSL 1.0.0.


       Copyright 2006-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (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>.