man 7ossl EVP_KEM-EC

EVP_KEM-EC(7ossl)                   OpenSSL                  EVP_KEM-EC(7ossl)

NAME
       EVP_KEM-EC - EVP_KEM EC keytype and algorithm support

DESCRIPTION
       The EC keytype and its parameters are described in EVP_PKEY-EC(7).  See
       EVP_PKEY_encapsulate(3) and EVP_PKEY_decapsulate(3) for more info.

   EC KEM parameters
       "operation" (OSSL_KEM_PARAM_OPERATION)<UTF8 string> 
           The OpenSSL EC Key Encapsulation Mechanisms only supports the
           following operation:

           "DHKEM" (OSSL_KEM_PARAM_OPERATION_DHKEM)
               The encapsulate function generates an ephemeral keypair. It
               produces keymaterial by doing an ECDH key exchange using the
               ephemeral private key and a supplied recipient public key. A
               HKDF operation using the keymaterial and a kem context then
               produces a shared secret. The shared secret and the ephemeral
               public key are returned.  The decapsulate function uses the
               recipient private key and the ephemeral public key to produce
               the same keymaterial, which can then be used to produce the
               same shared secret.  See
               <https://www.rfc-editor.org/rfc/rfc9180.html#name-dh-based-kem-dhkem> 

           This can be set using either EVP_PKEY_CTX_set_kem_op() or
           EVP_PKEY_CTX_set_params().

       "ikme" (OSSL_KEM_PARAM_IKME) <octet string> 
           Used to specify the key material used for generation of the
           ephemeral key.  This value should not be reused for other purposes.
           It can only be used for the curves "P-256", "P-384" and "P-521" and
           should have a length of at least the size of the encoded private
           key (i.e. 32, 48 and 66 for the listed curves).  If this value is
           not set, then a random ikm is used.

CONFORMING TO
       RFC9180

SEE ALSO
       EVP_PKEY_CTX_set_kem_op(3), EVP_PKEY_encapsulate(3),
       EVP_PKEY_decapsulate(3) EVP_KEYMGMT(3), EVP_PKEY(3),
       provider-keymgmt(7)

HISTORY
       This functionality was added in OpenSSL 3.2.

COPYRIGHT
       Copyright 2022 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>.

3.2.2                             2025-01-29                 EVP_KEM-EC(7ossl)