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.\" ========================================================================
.\"
.IX Title "EVP_PKEY_ENCAPSULATE 3"
.TH EVP_PKEY_ENCAPSULATE 3 "2023-05-30" "3.0.9" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
EVP_PKEY_encapsulate_init, EVP_PKEY_encapsulate
\&\- Key encapsulation using a public key algorithm
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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 *out, size_t *outlen,
\&                          unsigned char *genkey, size_t *genkeylen);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \fBEVP_PKEY_encapsulate_init()\fR function initializes a public key algorithm
context \fIctx\fR for an encapsulation operation and then sets the \fIparams\fR
on the context in the same way as calling \fBEVP_PKEY_CTX_set_params\fR\|(3).
.PP
The \fBEVP_PKEY_encapsulate()\fR function performs a public key encapsulation
operation using \fIctx\fR with the name \fIname\fR.
If \fIout\fR is \fB\s-1NULL\s0\fR then the maximum size of the output buffer is written to the
\&\fI*outlen\fR parameter and the maximum size of the generated key buffer is written
to \fI*genkeylen\fR. If \fIout\fR is not \fB\s-1NULL\s0\fR and the call is successful then the
internally generated key is written to \fIgenkey\fR and its size is written to
\&\fI*genkeylen\fR. The encapsulated version of the generated key is written to
\&\fIout\fR and its size is written to \fI*outlen\fR.
.SH "NOTES"
.IX Header "NOTES"
After the call to \fBEVP_PKEY_encapsulate_init()\fR algorithm specific parameters
for the operation may be set or modified using \fBEVP_PKEY_CTX_set_params\fR\|(3).
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBEVP_PKEY_encapsulate_init()\fR and \fBEVP_PKEY_encapsulate()\fR 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.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Encapsulate an \s-1RSASVE\s0 key (for \s-1RSA\s0 keys).
.PP
.Vb 1
\& #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 \*(AqRSASVE\*(Aq 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 \*(Aqsecret\*(Aq can be used as key material.
\&  * The encapsulated \*(Aqout\*(Aq can be sent to another party who can
\&  * decapsulate it using their private key to retrieve the \*(Aqsecret\*(Aq.
\&  */
\& if (EVP_PKEY_encapsulate(ctx, out, &outlen, secret, &secretlen) <= 0)
\&     /* Error */
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_PKEY_CTX_new\fR\|(3),
\&\fBEVP_PKEY_decapsulate\fR\|(3),
\&\s-1\fBEVP_KEM\-RSA\s0\fR\|(7),
.SH "HISTORY"
.IX Header "HISTORY"
These functions were added in OpenSSL 3.0.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2020\-2021 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.