| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | EVP_KEM-EC
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| 6 | - EVP_KEM EC keytype and algorithm support
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| 7 |
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| 8 | =head1 DESCRIPTION
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| 9 |
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| 10 | The B<EC> keytype and its parameters are described in L<EVP_PKEY-EC(7)>.
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| 11 | See L<EVP_PKEY_encapsulate(3)> and L<EVP_PKEY_decapsulate(3)> for more info.
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| 12 |
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| 13 | =head2 EC KEM parameters
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| 14 |
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| 15 | =over 4
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| 16 |
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| 17 | =item "operation" (B<OSSL_KEM_PARAM_OPERATION>)<UTF8 string>
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| 18 |
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| 19 | The OpenSSL EC Key Encapsulation Mechanisms only supports the
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| 20 | following operation:
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| 21 |
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| 22 | =over 4
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| 23 |
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| 24 | =item "DHKEM" (B<OSSL_KEM_PARAM_OPERATION_DHKEM>)
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| 25 |
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| 26 | The encapsulate function generates an ephemeral keypair. It produces keymaterial
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| 27 | by doing an ECDH key exchange using the ephemeral private key and a supplied
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| 28 | recipient public key. A HKDF operation using the keymaterial and a kem context
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| 29 | then produces a shared secret. The shared secret and the ephemeral public key
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| 30 | are returned.
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| 31 | The decapsulate function uses the recipient private key and the
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| 32 | ephemeral public key to produce the same keymaterial, which can then be used to
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| 33 | produce the same shared secret.
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| 34 | See L<https://www.rfc-editor.org/rfc/rfc9180.html#name-dh-based-kem-dhkem>
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| 35 |
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| 36 | =back
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| 37 |
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| 38 | This can be set using either EVP_PKEY_CTX_set_kem_op() or
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| 39 | EVP_PKEY_CTX_set_params().
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| 40 |
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| 41 | =item "ikme" (B<OSSL_KEM_PARAM_IKME>) <octet string>
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| 42 |
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| 43 | Used to specify the key material used for generation of the ephemeral key.
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| 44 | This value should not be reused for other purposes.
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| 45 | It can only be used for the curves "P-256", "P-384" and "P-521" and should
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| 46 | have a length of at least the size of the encoded private key
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| 47 | (i.e. 32, 48 and 66 for the listed curves).
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| 48 | If this value is not set, then a random ikm is used.
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| 49 |
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| 50 | =back
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| 51 |
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| 52 | =head1 CONFORMING TO
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| 53 |
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| 54 | =over 4
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| 55 |
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| 56 | =item RFC9180
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| 57 |
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| 58 | =back
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| 59 |
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| 60 | =head1 SEE ALSO
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| 61 |
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| 62 | L<EVP_PKEY_CTX_set_kem_op(3)>,
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| 63 | L<EVP_PKEY_encapsulate(3)>,
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| 64 | L<EVP_PKEY_decapsulate(3)>
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| 65 | L<EVP_KEYMGMT(3)>,
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| 66 | L<EVP_PKEY(3)>,
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| 67 | L<provider-keymgmt(7)>
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| 68 |
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| 69 | =head1 HISTORY
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| 70 |
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| 71 | This functionality was added in OpenSSL 3.2.
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| 72 |
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| 73 | =head1 COPYRIGHT
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| 74 |
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| 75 | Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
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| 76 |
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| 77 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 78 | this file except in compliance with the License. You can obtain a copy
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| 79 | in the file LICENSE in the source distribution or at
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| 80 | L<https://www.openssl.org/source/license.html>.
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| 81 |
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| 82 | =cut
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