1=pod 2 3=head1 NAME 4 5EVP_KEM-EC 6- EVP_KEM EC keytype and algorithm support 7 8=head1 DESCRIPTION 9 10The B<EC> keytype and its parameters are described in L<EVP_PKEY-EC(7)>. 11See L<EVP_PKEY_encapsulate(3)> and L<EVP_PKEY_decapsulate(3)> for more info. 12 13=head2 EC KEM parameters 14 15=over 4 16 17=item "operation" (B<OSSL_KEM_PARAM_OPERATION>)<UTF8 string> 18 19The OpenSSL EC Key Encapsulation Mechanisms only supports the 20following default operation (operating mode): 21 22=over 4 23 24=item "DHKEM" (B<OSSL_KEM_PARAM_OPERATION_DHKEM>) 25 26The encapsulate function generates an ephemeral keypair. It produces keymaterial 27by doing an ECDH key exchange using the ephemeral private key and a supplied 28recipient public key. A HKDF operation using the keymaterial and a kem context 29then produces a shared secret. The shared secret and the ephemeral public key 30are returned. 31The decapsulate function uses the recipient private key and the 32ephemeral public key to produce the same keymaterial, which can then be used to 33produce the same shared secret. 34See L<https://www.rfc-editor.org/rfc/rfc9180.html#name-dh-based-kem-dhkem> 35 36=back 37 38This can be set using either EVP_PKEY_CTX_set_kem_op() or 39EVP_PKEY_CTX_set_params(). 40 41=item "ikme" (B<OSSL_KEM_PARAM_IKME>) <octet string> 42 43Used to specify the key material used for generation of the ephemeral key. 44This value should not be reused for other purposes. 45It can only be used for the curves "P-256", "P-384" and "P-521" and should 46have a length of at least the size of the encoded private key 47(i.e. 32, 48 and 66 for the listed curves). 48If this value is not set, then a random ikm is used. 49 50=back 51 52=head1 CONFORMING TO 53 54=over 4 55 56=item RFC9180 57 58=back 59 60=head1 SEE ALSO 61 62L<EVP_PKEY_CTX_set_kem_op(3)>, 63L<EVP_PKEY_encapsulate(3)>, 64L<EVP_PKEY_decapsulate(3)> 65L<EVP_KEYMGMT(3)>, 66L<EVP_PKEY(3)>, 67L<provider-keymgmt(7)> 68 69=head1 HISTORY 70 71This functionality was added in OpenSSL 3.2. 72 73The C<operation> (operating mode) was a required parameter prior to OpenSSL 3.5. 74As of OpenSSL 3.5, C<DHKEM> is the default operating mode, and no explicit value 75need be specified. 76 77=head1 COPYRIGHT 78 79Copyright 2022-2025 The OpenSSL Project Authors. All Rights Reserved. 80 81Licensed under the Apache License 2.0 (the "License"). You may not use 82this file except in compliance with the License. You can obtain a copy 83in the file LICENSE in the source distribution or at 84L<https://www.openssl.org/source/license.html>. 85 86=cut 87