Updated: 2022/Sep/29

Please read Privacy Policy. It's for your privacy.

EVP_PKEY_encapsulate(3)             OpenSSL            EVP_PKEY_encapsulate(3)



NAME
       EVP_PKEY_encapsulate_init, EVP_PKEY_encapsulate - Key encapsulation
       using a KEM algorithm with a public key

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #include <openssl/evp.h>

        int EVP_PKEY_encapsulate_init(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]);
        int EVP_PKEY_encapsulate(EVP_PKEY_CTX *ctx,
                                 unsigned char *wrappedkey, size_t *wrappedkeylen,
                                 unsigned char *genkey, size_t *genkeylen);

DESCRIPTION
       The EVP_PKEY_encapsulate_init() function initializes a public key
       algorithm context ctx for an encapsulation operation and then sets the
       params on the context in the same way as calling
       EVP_PKEY_CTX_set_params(3).  Note that ctx is usually is produced using
       EVP_PKEY_CTX_new_from_pkey(3), specifying the public key to use.

       The EVP_PKEY_encapsulate() function performs a public key encapsulation
       operation using ctx.  The symmetric secret generated in genkey can be
       used as key material.  The ciphertext in wrappedkey is its encapsulated
       form, which can be sent to another party, who can use
       EVP_PKEY_decapsulate(3) to retrieve it using their private key.  If
       wrappedkey is NULL then the maximum size of the output buffer is
       written to the *wrappedkeylen parameter unless wrappedkeylen is NULL
       and the maximum size of the generated key buffer is written to
       *genkeylen unless genkeylen is NULL. If wrappedkey is not NULL and the
       call is successful then the internally generated key is written to
       genkey and its size is written to *genkeylen. The encapsulated version
       of the generated key is written to wrappedkey and its size is written
       to *wrappedkeylen.

NOTES
       After the call to EVP_PKEY_encapsulate_init() algorithm-specific
       parameters for the operation may be set or modified using
       EVP_PKEY_CTX_set_params(3).

RETURN VALUES
       EVP_PKEY_encapsulate_init() and EVP_PKEY_encapsulate() return 1 for
       success and 0 or a negative value for failure. In particular a return
       value of -2 indicates the operation is not supported by the public key
       algorithm.

EXAMPLES
       Encapsulate an RSASVE key (for RSA keys).

        #include <openssl/evp.h>

        /*
         * NB: assumes rsa_pub_key is an public key of another party.
         */

        EVP_PKEY_CTX *ctx = NULL;
        size_t secretlen = 0, outlen = 0;
        unsigned char *out = NULL, *secret = NULL;

        ctx = EVP_PKEY_CTX_new_from_pkey(libctx, rsa_pub_key, NULL);
        if (ctx = NULL)
            /* Error */
        if (EVP_PKEY_encapsulate_init(ctx, NULL) <= 0)
            /* Error */

        /* Set the mode - only 'RSASVE' is currently supported */
         if (EVP_PKEY_CTX_set_kem_op(ctx, "RSASVE") <= 0)
            /* Error */
        /* Determine buffer length */
        if (EVP_PKEY_encapsulate(ctx, NULL, &outlen, NULL, &secretlen) <= 0)
            /* Error */

        out = OPENSSL_malloc(outlen);
        secret = OPENSSL_malloc(secretlen);
        if (out == NULL || secret == NULL)
            /* malloc failure */

        /*
         * The generated 'secret' can be used as key material.
         * The encapsulated 'out' can be sent to another party who can
         * decapsulate it using their private key to retrieve the 'secret'.
         */
        if (EVP_PKEY_encapsulate(ctx, out, &outlen, secret, &secretlen) <= 0)
            /* Error */

SEE ALSO
       EVP_PKEY_CTX_new_from_pkey(3), EVP_PKEY_decapsulate(3), EVP_KEM-RSA(7),

HISTORY
       These functions were added in OpenSSL 3.0.

COPYRIGHT
       Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.



3.0.12                            2023-10-25           EVP_PKEY_encapsulate(3)