doc/man3/EVP_PKEY_decapsulate.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 EVP_PKEY_decapsulate_init, EVP_PKEY_auth_decapsulate_init, EVP_PKEY_decapsulate
   6 - Key decapsulation using a private key algorithm
   7
   8 =head1 SYNOPSIS
   9
  10  #include <openssl/evp.h>
  11
  12  int EVP_PKEY_decapsulate_init(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]);
  13  int EVP_PKEY_auth_decapsulate_init(EVP_PKEY_CTX *ctx, EVP_PKEY *authpub,
  14                                    const OSSL_PARAM params[]);
  15  int EVP_PKEY_decapsulate(EVP_PKEY_CTX *ctx,
  16                           unsigned char *secret, size_t *secretlen,
  17                           const unsigned char *wrapped, size_t wrappedlen);
  18
  19 =head1 DESCRIPTION
  20
  21 The EVP_PKEY_decapsulate_init() function initializes a private key algorithm
  22 context I<ctx> for a decapsulation operation and then sets the I<params>
  23 on the context in the same way as calling L<EVP_PKEY_CTX_set_params(3)>.
  24
  25 The EVP_PKEY_auth_decapsulate_init() function is similiar to
  26 EVP_PKEY_decapsulate_init() but also passes an I<authpub> authentication public
  27 key that is used during decapsulation.
  28
  29 The EVP_PKEY_decapsulate() function performs a private key decapsulation
  30 operation using I<ctx>. The data to be decapsulated is specified using the
  31 I<wrapped> and I<wrappedlen> parameters.
  32 If I<secret> is I<NULL> then the maximum size of the output secret buffer
  33 is written to the I<*secretlen> parameter. If I<secret> is not B<NULL> and the
  34 call is successful then the decapsulated secret data is written to I<secret> and
  35 the amount of data written to I<secretlen>.
  36
  37 =head1 NOTES
  38
  39 After the call to EVP_PKEY_decapsulate_init() algorithm specific parameters
  40 for the operation may be set or modified using L<EVP_PKEY_CTX_set_params(3)>.
  41
  42 =head1 RETURN VALUES
  43
  44 EVP_PKEY_decapsulate_init(), EVP_PKEY_auth_decapsulate_init() and
  45 EVP_PKEY_decapsulate() return 1 for success and 0 or a negative value for
  46 failure. In particular a return value of -2 indicates the operation is not
  47 supported by the private key algorithm.
  48
  49 =head1 EXAMPLES
  50
  51 Decapsulate data using RSA:
  52
  53  #include <openssl/evp.h>
  54
  55  /*
  56   * NB: assumes rsa_priv_key is an RSA private key,
  57   * and that in, inlen are already set up to contain encapsulated data.
  58   */
  59
  60  EVP_PKEY_CTX *ctx = NULL;
  61  size_t secretlen = 0;
  62  unsigned char *secret = NULL;;
  63
  64  ctx = EVP_PKEY_CTX_new_from_pkey(libctx, rsa_priv_key, NULL);
  65  if (ctx = NULL)
  66      /* Error */
  67  if (EVP_PKEY_decapsulate_init(ctx, NULL) <= 0)
  68      /* Error */
  69
  70  /* Set the mode - only 'RSASVE' is currently supported */
  71  if (EVP_PKEY_CTX_set_kem_op(ctx, "RSASVE") <= 0)
  72      /* Error */
  73
  74  /* Determine buffer length */
  75  if (EVP_PKEY_decapsulate(ctx, NULL, &secretlen, in, inlen) <= 0)
  76      /* Error */
  77
  78  secret = OPENSSL_malloc(secretlen);
  79  if (secret == NULL)
  80      /* malloc failure */
  81
  82  /* Decapsulated secret data is secretlen bytes long */
  83  if (EVP_PKEY_decapsulate(ctx, secret, &secretlen, in, inlen) <= 0)
  84      /* Error */
  85
  86
  87 =head1 SEE ALSO
  88
  89 L<EVP_PKEY_CTX_new(3)>,
  90 L<EVP_PKEY_encapsulate(3)>,
  91 L<EVP_KEM-RSA(7)>, L<EVP_KEM-X25519(7)>, L<EVP_KEM-EC(7)>
  92
  93 =head1 HISTORY
  94
  95 The functions EVP_PKEY_decapsulate_init() and EVP_PKEY_decapsulate() were added
  96 in OpenSSL 3.0.
  97
  98 The function EVP_PKEY_auth_decapsulate_init() was added in OpenSSL 3.2.
  99
 100 =head1 COPYRIGHT
 101
 102 Copyright 2020-2022 The OpenSSL Project Authors. All Rights Reserved.
 103
 104 Licensed under the Apache License 2.0 (the "License").  You may not use
 105 this file except in compliance with the License.  You can obtain a copy
 106 in the file LICENSE in the source distribution or at
 107 L<https://www.openssl.org/source/license.html>.
 108
 109 =cut