2022-08-26 09:54:35 +08:00
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=pod
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=head1 NAME
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EVP_KEM-X25519, EVP_KEM-X448
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- EVP_KEM X25519 and EVP_KEM X448 keytype and algorithm support
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=head1 DESCRIPTION
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The B<X25519> and <X448> keytype and its parameters are described in
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L<EVP_PKEY-X25519(7)>.
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See L<EVP_PKEY_encapsulate(3)> and L<EVP_PKEY_decapsulate(3)> for more info.
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=head2 X25519 and X448 KEM parameters
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=over 4
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=item "operation" (B<OSSL_KEM_PARAM_OPERATION>)<UTF8 string>
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The OpenSSL X25519 and X448 Key Encapsulation Mechanisms only support the
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following operation:
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=over 4
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=item "DHKEM" (B<OSSL_KEM_PARAM_OPERATION_DHKEM>)
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The encapsulate function generates an ephemeral keypair. It produces keymaterial
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by doing an X25519 or X448 key exchange using the ephemeral private key and a
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supplied recipient public key. A HKDF operation using the keymaterial and a kem
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context then produces a shared secret. The shared secret and the ephemeral
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public key are returned.
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The decapsulate function uses the recipient private key and the
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ephemeral public key to produce the same keymaterial, which can then be used to
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produce the same shared secret.
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See L<https://www.rfc-editor.org/rfc/rfc9180.html#name-dh-based-kem-dhkem>
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=back
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This can be set using either EVP_PKEY_CTX_set_kem_op() or
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EVP_PKEY_CTX_set_params().
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=item "ikme" (B<OSSL_KEM_PARAM_IKME>) <octet string>
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Used to specify the key material used for generation of the ephemeral key.
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This value should not be reused for other purposes.
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It should have a length of at least 32 for X25519, and 56 for X448.
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If this value is not set, then a random ikm is used.
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=back
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=head1 CONFORMING TO
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=over 4
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=item RFC9180
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=back
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=head1 SEE ALSO
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L<EVP_PKEY_CTX_set_kem_op(3)>,
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L<EVP_PKEY_encapsulate(3)>,
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L<EVP_PKEY_decapsulate(3)>
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L<EVP_KEYMGMT(3)>,
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L<EVP_PKEY(3)>,
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L<provider-keymgmt(7)>
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2022-11-17 05:26:06 +08:00
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=head1 HISTORY
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2022-11-21 19:11:02 +08:00
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This functionality was added in OpenSSL 3.2.
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2022-11-17 05:26:06 +08:00
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2022-08-26 09:54:35 +08:00
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=head1 COPYRIGHT
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Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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