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112 lines
3.6 KiB
Plaintext
112 lines
3.6 KiB
Plaintext
=pod
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=head1 NAME
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EVP_PKEY_decapsulate_init, EVP_PKEY_auth_decapsulate_init, EVP_PKEY_decapsulate
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- Key decapsulation using a KEM algorithm with a private key
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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int EVP_PKEY_decapsulate_init(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]);
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int EVP_PKEY_auth_decapsulate_init(EVP_PKEY_CTX *ctx, EVP_PKEY *authpub,
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const OSSL_PARAM params[]);
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int EVP_PKEY_decapsulate(EVP_PKEY_CTX *ctx,
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unsigned char *unwrapped, size_t *unwrappedlen,
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const unsigned char *wrapped, size_t wrappedlen);
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=head1 DESCRIPTION
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The EVP_PKEY_decapsulate_init() function initializes a private key algorithm
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context I<ctx> for a decapsulation operation and then sets the I<params>
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on the context in the same way as calling L<EVP_PKEY_CTX_set_params(3)>.
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Note that I<ctx> usually is produced using L<EVP_PKEY_CTX_new_from_pkey(3)>,
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specifying the private key to use.
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The EVP_PKEY_auth_decapsulate_init() function is similar to
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EVP_PKEY_decapsulate_init() but also passes an I<authpub> authentication public
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key that is used during decapsulation.
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The EVP_PKEY_decapsulate() function performs a private key decapsulation
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operation using I<ctx>. The data to be decapsulated is specified using the
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I<wrapped> and I<wrappedlen> parameters.
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If I<unwrapped> is NULL then the maximum size of the output secret buffer
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is written to I<*unwrappedlen>. If I<unwrapped> is not NULL and the
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call is successful then the decapsulated secret data is written to I<unwrapped>
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and the amount of data written to I<*unwrappedlen>.
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=head1 NOTES
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After the call to EVP_PKEY_decapsulate_init() algorithm-specific parameters
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for the operation may be set or modified using L<EVP_PKEY_CTX_set_params(3)>.
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=head1 RETURN VALUES
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EVP_PKEY_decapsulate_init(), EVP_PKEY_auth_decapsulate_init() and
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EVP_PKEY_decapsulate() return 1 for success and 0 or a negative value for
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failure. In particular a return value of -2 indicates the operation is not
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supported by the private key algorithm.
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=head1 EXAMPLES
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Decapsulate data using RSA:
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#include <openssl/evp.h>
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/*
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* NB: assumes rsa_priv_key is an RSA private key,
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* and that in, inlen are already set up to contain encapsulated data.
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*/
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EVP_PKEY_CTX *ctx = NULL;
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size_t secretlen = 0;
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unsigned char *secret = NULL;;
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ctx = EVP_PKEY_CTX_new_from_pkey(libctx, rsa_priv_key, NULL);
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if (ctx = NULL)
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/* Error */
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if (EVP_PKEY_decapsulate_init(ctx, NULL) <= 0)
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/* Error */
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/* Set the mode - only 'RSASVE' is currently supported */
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if (EVP_PKEY_CTX_set_kem_op(ctx, "RSASVE") <= 0)
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/* Error */
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/* Determine buffer length */
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if (EVP_PKEY_decapsulate(ctx, NULL, &secretlen, in, inlen) <= 0)
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/* Error */
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secret = OPENSSL_malloc(secretlen);
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if (secret == NULL)
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/* malloc failure */
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/* Decapsulated secret data is secretlen bytes long */
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if (EVP_PKEY_decapsulate(ctx, secret, &secretlen, in, inlen) <= 0)
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/* Error */
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=head1 SEE ALSO
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L<EVP_PKEY_CTX_new_from_pkey(3)>,
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L<EVP_PKEY_encapsulate(3)>,
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L<EVP_KEM-RSA(7)>, L<EVP_KEM-X25519(7)>, L<EVP_KEM-EC(7)>
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=head1 HISTORY
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The functions EVP_PKEY_decapsulate_init() and EVP_PKEY_decapsulate() were added
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in OpenSSL 3.0.
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The function EVP_PKEY_auth_decapsulate_init() was added in OpenSSL 3.2.
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=head1 COPYRIGHT
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Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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