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