1=pod 2 3=head1 NAME 4 5EVP_PKEY_encapsulate_init, EVP_PKEY_auth_encapsulate_init, EVP_PKEY_encapsulate 6- Key encapsulation using a KEM algorithm with a public key 7 8=head1 SYNOPSIS 9 10 #include <openssl/evp.h> 11 12 int EVP_PKEY_encapsulate_init(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]); 13 int EVP_PKEY_auth_encapsulate_init(EVP_PKEY_CTX *ctx, EVP_PKEY *authpriv, 14 const OSSL_PARAM params[]); 15 int EVP_PKEY_encapsulate(EVP_PKEY_CTX *ctx, 16 unsigned char *wrappedkey, size_t *wrappedkeylen, 17 unsigned char *genkey, size_t *genkeylen); 18 19=head1 DESCRIPTION 20 21The EVP_PKEY_encapsulate_init() function initializes a public key algorithm 22context I<ctx> for an encapsulation operation and then sets the I<params> 23on the context in the same way as calling L<EVP_PKEY_CTX_set_params(3)>. 24Note that I<ctx> is usually is produced using L<EVP_PKEY_CTX_new_from_pkey(3)>, 25specifying the public key to use. 26 27The EVP_PKEY_auth_encapsulate_init() function is similar to 28EVP_PKEY_encapsulate_init() but also passes an I<authpriv> authentication private 29key that is used during encapsulation. 30 31The EVP_PKEY_encapsulate() function performs a public key encapsulation 32operation using I<ctx>. 33The symmetric secret generated in I<genkey> can be used as key material. 34The ciphertext in I<wrappedkey> is its encapsulated form, which can be sent 35to another party, who can use L<EVP_PKEY_decapsulate(3)> to retrieve it 36using their private key. 37If I<wrappedkey> is NULL then the maximum size of the output buffer 38is written to the I<*wrappedkeylen> parameter unless I<wrappedkeylen> is NULL 39and the maximum size of the generated key buffer is written to I<*genkeylen> 40unless I<genkeylen> is NULL. 41If I<wrappedkey> is not NULL and the call is successful then the 42internally generated key is written to I<genkey> and its size is written to 43I<*genkeylen>. The encapsulated version of the generated key is written to 44I<wrappedkey> and its size is written to I<*wrappedkeylen>. Note that if 45I<wrappedlen> is not NULL, then the value it points to must initially hold the size of 46the I<unwrapped> buffer so that its size can be validated by the call, ensuring 47it is large enough to hold the result written to I<wrapped>. 48 49=head1 NOTES 50 51After the call to EVP_PKEY_encapsulate_init() algorithm-specific parameters 52for the operation may be set or modified using L<EVP_PKEY_CTX_set_params(3)>. 53 54=head1 RETURN VALUES 55 56EVP_PKEY_encapsulate_init(), EVP_PKEY_auth_encapsulate_init() and 57EVP_PKEY_encapsulate() return 1 for success and 0 or a negative value for 58failure. In particular a return value of -2 indicates the operation is not 59supported by the public key algorithm. 60 61=head1 EXAMPLES 62 63Encapsulate an RSASVE key (for RSA keys). 64 65 #include <openssl/evp.h> 66 67 /* 68 * NB: assumes rsa_pub_key is an public key of another party. 69 */ 70 71 EVP_PKEY_CTX *ctx = NULL; 72 size_t secretlen = 0, outlen = 0; 73 unsigned char *out = NULL, *secret = NULL; 74 75 ctx = EVP_PKEY_CTX_new_from_pkey(libctx, rsa_pub_key, NULL); 76 if (ctx == NULL) 77 /* Error */ 78 if (EVP_PKEY_encapsulate_init(ctx, NULL) <= 0) 79 /* Error */ 80 81 /* Set the mode - only 'RSASVE' is currently supported */ 82 if (EVP_PKEY_CTX_set_kem_op(ctx, "RSASVE") <= 0) 83 /* Error */ 84 /* Determine buffer length */ 85 if (EVP_PKEY_encapsulate(ctx, NULL, &outlen, NULL, &secretlen) <= 0) 86 /* Error */ 87 88 out = OPENSSL_malloc(outlen); 89 secret = OPENSSL_malloc(secretlen); 90 if (out == NULL || secret == NULL) 91 /* malloc failure */ 92 93 /* 94 * The generated 'secret' can be used as key material. 95 * The encapsulated 'out' can be sent to another party who can 96 * decapsulate it using their private key to retrieve the 'secret'. 97 */ 98 if (EVP_PKEY_encapsulate(ctx, out, &outlen, secret, &secretlen) <= 0) 99 /* Error */ 100 101=head1 SEE ALSO 102 103L<EVP_PKEY_CTX_new_from_pkey(3)>, 104L<EVP_PKEY_decapsulate(3)>, 105L<EVP_KEM-RSA(7)>, L<EVP_KEM-X25519(7)>, L<EVP_KEM-EC(7)> 106 107=head1 HISTORY 108 109These functions EVP_PKEY_encapsulate_init() and EVP_PKEY_encapsulate() were 110added in OpenSSL 3.0. 111The function EVP_PKEY_auth_encapsulate_init() was added in OpenSSL 3.2. 112 113=head1 COPYRIGHT 114 115Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved. 116 117Licensed under the Apache License 2.0 (the "License"). You may not use 118this file except in compliance with the License. You can obtain a copy 119in the file LICENSE in the source distribution or at 120L<https://www.openssl.org/source/license.html>. 121 122=cut 123
