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>. 45 46=head1 NOTES 47 48After the call to EVP_PKEY_encapsulate_init() algorithm-specific parameters 49for the operation may be set or modified using L<EVP_PKEY_CTX_set_params(3)>. 50 51=head1 RETURN VALUES 52 53EVP_PKEY_encapsulate_init(), EVP_PKEY_auth_encapsulate_init() and 54EVP_PKEY_encapsulate() return 1 for success and 0 or a negative value for 55failure. In particular a return value of -2 indicates the operation is not 56supported by the public key algorithm. 57 58=head1 EXAMPLES 59 60Encapsulate an RSASVE key (for RSA keys). 61 62 #include <openssl/evp.h> 63 64 /* 65 * NB: assumes rsa_pub_key is an public key of another party. 66 */ 67 68 EVP_PKEY_CTX *ctx = NULL; 69 size_t secretlen = 0, outlen = 0; 70 unsigned char *out = NULL, *secret = NULL; 71 72 ctx = EVP_PKEY_CTX_new_from_pkey(libctx, rsa_pub_key, NULL); 73 if (ctx = NULL) 74 /* Error */ 75 if (EVP_PKEY_encapsulate_init(ctx, NULL) <= 0) 76 /* Error */ 77 78 /* Set the mode - only 'RSASVE' is currently supported */ 79 if (EVP_PKEY_CTX_set_kem_op(ctx, "RSASVE") <= 0) 80 /* Error */ 81 /* Determine buffer length */ 82 if (EVP_PKEY_encapsulate(ctx, NULL, &outlen, NULL, &secretlen) <= 0) 83 /* Error */ 84 85 out = OPENSSL_malloc(outlen); 86 secret = OPENSSL_malloc(secretlen); 87 if (out == NULL || secret == NULL) 88 /* malloc failure */ 89 90 /* 91 * The generated 'secret' can be used as key material. 92 * The encapsulated 'out' can be sent to another party who can 93 * decapsulate it using their private key to retrieve the 'secret'. 94 */ 95 if (EVP_PKEY_encapsulate(ctx, out, &outlen, secret, &secretlen) <= 0) 96 /* Error */ 97 98=head1 SEE ALSO 99 100L<EVP_PKEY_CTX_new_from_pkey(3)>, 101L<EVP_PKEY_decapsulate(3)>, 102L<EVP_KEM-RSA(7)>, L<EVP_KEM-X25519(7)>, L<EVP_KEM-EC(7)> 103 104=head1 HISTORY 105 106These functions EVP_PKEY_encapsulate_init() and EVP_PKEY_encapsulate() were 107added in OpenSSL 3.0. 108The function EVP_PKEY_auth_encapsulate_init() was added in OpenSSL 3.2. 109 110=head1 COPYRIGHT 111 112Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved. 113 114Licensed under the Apache License 2.0 (the "License"). You may not use 115this file except in compliance with the License. You can obtain a copy 116in the file LICENSE in the source distribution or at 117L<https://www.openssl.org/source/license.html>. 118 119=cut 120
