openssl/doc/man3/EVP_PKEY_encapsulate.pod
Shane Lontis 80f4fd18f7 Add KEM (Key encapsulation mechanism) support to providers
SP800-56Br2 requires support for the RSA primitives for RSASVE generate and recover.
As these are simple KEM operations another operation type has been added that can support future extensions.

Added public functions EVP_PKEY_encapsulate_init(), EVP_PKEY_encapsulate(), EVP_PKEY_decapsulate_init() and EVP_PKEY_decapsulate()
Added EVP_KEM_* functions.
Added OSSL_FUNC_kem_* dispatch functions

Added EVP_PKEY_CTX_set_kem_op() so that different types of KEM can be added in the future. This value must currently be set to
"RSASVE" after EVP_PKEY_encapsulate_init() & EVP_PKEY_decapsulate_init() as there is no default value.
This allows the existing RSA key types, keymanagers, and encoders to be used with the encapsulation operations.

The design of the public API's resulted from contributions from @romen & @levitte.

Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/12750)
2020-09-19 18:08:46 +10:00

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=pod
=head1 NAME
EVP_PKEY_encapsulate_init, EVP_PKEY_encapsulate
- Key encapsulation using a public key algorithm
=head1 SYNOPSIS
#include <openssl/evp.h>
int EVP_PKEY_encapsulate_init(EVP_PKEY_CTX *ctx);
int EVP_PKEY_encapsulate(EVP_PKEY_CTX *ctx,
unsigned char *out, size_t *outlen,
unsigned char *genkey, size_t *genkeylen);
=head1 DESCRIPTION
The EVP_PKEY_encapsulate_init() function initializes a public key algorithm
context I<ctx> for an encapsulation operation.
The EVP_PKEY_encapsulate() function performs a public key encapsulation
operation using I<ctx> with the name I<name>.
If I<out> is B<NULL> then the maximum size of the output buffer is written to the
I<*outlen> parameter and the maximum size of the generated key buffer is written
to I<*genkeylen>. If I<out> is not B<NULL> and the call is successful then the
internally generated key is written to I<genkey> and its size is written to
I<*genkeylen>. The encapsulated version of the generated key is written to
I<out> and its size is written to I<*outlen>.
=head1 NOTES
After the call to EVP_PKEY_encapsulate_init() algorithm specific parameters
for the operation may be set using L<EVP_PKEY_CTX_set_params(3)>.
=head1 RETURN VALUES
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.
=head1 EXAMPLES
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) <= 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 */
=head1 SEE ALSO
L<EVP_PKEY_CTX_new(3)>,
L<EVP_PKEY_decapsulate(3)>,
L<EVP_KEM-RSA(7)>,
=head1 HISTORY
These functions were added in OpenSSL 3.0.
=head1 COPYRIGHT
Copyright 2020 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
L<https://www.openssl.org/source/license.html>.
=cut