EVP_PKEY_encapsulate_init, EVP_PKEY_encapsulate - Key encapsulation using a KEM
algorithm with a public key
#include <openssl/evp.h>
int EVP_PKEY_encapsulate_init(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]);
int EVP_PKEY_encapsulate(EVP_PKEY_CTX *ctx,
unsigned char *wrappedkey, size_t *wrappedkeylen,
unsigned char *genkey, size_t *genkeylen);
The
EVP_PKEY_encapsulate_init() function initializes a public key
algorithm context
ctx for an encapsulation operation and then sets the
params on the context in the same way as calling
EVP_PKEY_CTX_set_params(3). Note that
ctx is usually is produced
using
EVP_PKEY_CTX_new_from_pkey(3), specifying the public key to use.
The
EVP_PKEY_encapsulate() function performs a public key encapsulation
operation using
ctx. The symmetric secret generated in
genkey
can be used as key material. The ciphertext in
wrappedkey is its
encapsulated form, which can be sent to another party, who can use
EVP_PKEY_decapsulate(3) to retrieve it using their private key. If
wrappedkey is NULL then the maximum size of the output buffer is
written to the
*wrappedkeylen parameter unless
wrappedkeylen is
NULL and the maximum size of the generated key buffer is written to
*genkeylen unless
genkeylen is NULL. If
wrappedkey is not
NULL and the call is successful then the internally generated key is written
to
genkey and its size is written to
*genkeylen. The
encapsulated version of the generated key is written to
wrappedkey and
its size is written to
*wrappedkeylen.
After the call to
EVP_PKEY_encapsulate_init() algorithm-specific
parameters for the operation may be set or modified using
EVP_PKEY_CTX_set_params(3).
EVP_PKEY_encapsulate_init() and
EVP_PKEY_encapsulate() 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.
Encapsulate an RSASVE key (for RSA keys).
#include <openssl/evp.h>
/*
* NB: assumes rsa_pub_key is an public key of another party.
*/
EVP_PKEY_CTX *ctx = NULL;
size_t secretlen = 0, outlen = 0;
unsigned char *out = NULL, *secret = NULL;
ctx = EVP_PKEY_CTX_new_from_pkey(libctx, rsa_pub_key, NULL);
if (ctx = NULL)
/* Error */
if (EVP_PKEY_encapsulate_init(ctx, NULL) <= 0)
/* Error */
/* Set the mode - only 'RSASVE' is currently supported */
if (EVP_PKEY_CTX_set_kem_op(ctx, "RSASVE") <= 0)
/* Error */
/* Determine buffer length */
if (EVP_PKEY_encapsulate(ctx, NULL, &outlen, NULL, &secretlen) <= 0)
/* Error */
out = OPENSSL_malloc(outlen);
secret = OPENSSL_malloc(secretlen);
if (out == NULL || secret == NULL)
/* malloc failure */
/*
* The generated 'secret' can be used as key material.
* The encapsulated 'out' can be sent to another party who can
* decapsulate it using their private key to retrieve the 'secret'.
*/
if (EVP_PKEY_encapsulate(ctx, out, &outlen, secret, &secretlen) <= 0)
/* Error */
EVP_PKEY_CTX_new_from_pkey(3),
EVP_PKEY_decapsulate(3),
EVP_KEM-RSA(7),
These functions were added in OpenSSL 3.0.
Copyright 2020-2023 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>.