83 lines
2.7 KiB
Plaintext
83 lines
2.7 KiB
Plaintext
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=pod
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=head1 NAME
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DH_generate_key, DH_compute_key, DH_compute_key_padded - perform
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Diffie-Hellman key exchange
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=head1 SYNOPSIS
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#include <openssl/dh.h>
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The following functions have been deprecated since OpenSSL 3.0, and can be
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hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
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see L<openssl_user_macros(7)>:
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int DH_generate_key(DH *dh);
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int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
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int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh);
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=head1 DESCRIPTION
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All of the functions described on this page are deprecated.
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Applications should instead use L<EVP_PKEY_derive_init(3)>
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and L<EVP_PKEY_derive(3)>.
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DH_generate_key() performs the first step of a Diffie-Hellman key
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exchange by generating private and public DH values. By calling
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DH_compute_key() or DH_compute_key_padded(), these are combined with
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the other party's public value to compute the shared key.
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DH_generate_key() expects B<dh> to contain the shared parameters
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B<dh-E<gt>p> and B<dh-E<gt>g>. It generates a random private DH value
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unless B<dh-E<gt>priv_key> is already set, and computes the
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corresponding public value B<dh-E<gt>pub_key>, which can then be
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published.
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DH_compute_key() computes the shared secret from the private DH value
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in B<dh> and the other party's public value in B<pub_key> and stores
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it in B<key>. B<key> must point to B<DH_size(dh)> bytes of memory.
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The padding style is RFC 5246 (8.1.2) that strips leading zero bytes.
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It is not constant time due to the leading zero bytes being stripped.
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The return value should be considered public.
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DH_compute_key_padded() is similar but stores a fixed number of bytes.
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The padding style is NIST SP 800-56A (C.1) that retains leading zero bytes.
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It is constant time due to the leading zero bytes being retained.
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The return value should be considered public.
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=head1 RETURN VALUES
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DH_generate_key() returns 1 on success, 0 otherwise.
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DH_compute_key() returns the size of the shared secret on success, -1
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on error.
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DH_compute_key_padded() returns B<DH_size(dh)> on success, -1 on error.
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The error codes can be obtained by L<ERR_get_error(3)>.
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=head1 SEE ALSO
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L<EVP_PKEY_derive(3)>,
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L<DH_new(3)>, L<ERR_get_error(3)>, L<RAND_bytes(3)>, L<DH_size(3)>
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=head1 HISTORY
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DH_compute_key_padded() was added in OpenSSL 1.0.2.
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All of these functions were deprecated in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2000-2021 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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