1EVP_PKEY_DECAPSULATE(3ossl)         OpenSSL        EVP_PKEY_DECAPSULATE(3ossl)
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NAME

6       EVP_PKEY_decapsulate_init, EVP_PKEY_decapsulate - Key decapsulation
7       using a private key algorithm
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SYNOPSIS

10        #include <openssl/evp.h>
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12        int EVP_PKEY_decapsulate_init(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]);
13        int EVP_PKEY_decapsulate(EVP_PKEY_CTX *ctx,
14                                 unsigned char *secret, size_t *secretlen,
15                                 const unsigned char *wrapped, size_t wrappedlen);
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DESCRIPTION

18       The EVP_PKEY_decapsulate_init() function initializes a private key
19       algorithm context ctx for a decapsulation operation and then sets the
20       params on the context in the same way as calling
21       EVP_PKEY_CTX_set_params(3).
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23       The EVP_PKEY_decapsulate() function performs a private key
24       decapsulation operation using ctx. The data to be decapsulated is
25       specified using the wrapped and wrappedlen parameters.  If secret is
26       NULL then the maximum size of the output secret buffer is written to
27       the *secretlen parameter. If secret is not NULL and the call is
28       successful then the decapsulated secret data is written to secret and
29       the amount of data written to secretlen.
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NOTES

32       After the call to EVP_PKEY_decapsulate_init() algorithm specific
33       parameters for the operation may be set or modified using
34       EVP_PKEY_CTX_set_params(3).
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RETURN VALUES

37       EVP_PKEY_decapsulate_init() and EVP_PKEY_decapsulate() return 1 for
38       success and 0 or a negative value for failure. In particular a return
39       value of -2 indicates the operation is not supported by the private key
40       algorithm.
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EXAMPLES

43       Decapsulate data using RSA:
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45        #include <openssl/evp.h>
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47        /*
48         * NB: assumes rsa_priv_key is an RSA private key,
49         * and that in, inlen are already set up to contain encapsulated data.
50         */
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52        EVP_PKEY_CTX *ctx = NULL;
53        size_t secretlen = 0;
54        unsigned char *secret = NULL;;
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56        ctx = EVP_PKEY_CTX_new_from_pkey(libctx, rsa_priv_key, NULL);
57        if (ctx = NULL)
58            /* Error */
59        if (EVP_PKEY_decapsulate_init(ctx, NULL) <= 0)
60            /* Error */
61
62        /* Set the mode - only 'RSASVE' is currently supported */
63        if (EVP_PKEY_CTX_set_kem_op(ctx, "RSASVE") <= 0)
64            /* Error */
65
66        /* Determine buffer length */
67        if (EVP_PKEY_decapsulate(ctx, NULL, &secretlen, in, inlen) <= 0)
68            /* Error */
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70        secret = OPENSSL_malloc(secretlen);
71        if (secret == NULL)
72            /* malloc failure */
73
74        /* Decapsulated secret data is secretlen bytes long */
75        if (EVP_PKEY_decapsulaterctx, secret, &secretlen, in, inlen) <= 0)
76            /* Error */
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SEE ALSO

79       EVP_PKEY_CTX_new(3), EVP_PKEY_encapsulate(3), EVP_KEM-RSA(7),
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HISTORY

82       These functions were added in OpenSSL 3.0.
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85       Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
86
87       Licensed under the Apache License 2.0 (the "License").  You may not use
88       this file except in compliance with the License.  You can obtain a copy
89       in the file LICENSE in the source distribution or at
90       <https://www.openssl.org/source/license.html>.
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943.1.1                             2023-08-31       EVP_PKEY_DECAPSULATE(3ossl)
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