134 lines
3.6 KiB
Text
134 lines
3.6 KiB
Text
=pod
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=head1 NAME
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DH_generate_parameters_ex, DH_generate_parameters,
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DH_check, DH_check_params - generate and check Diffie-Hellman
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parameters
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=head1 SYNOPSIS
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#include <openssl/dh.h>
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int DH_generate_parameters_ex(DH *dh, int prime_len, int generator, BN_GENCB *cb);
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int DH_check(DH *dh, int *codes);
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int DH_check_params(DH *dh, int *codes);
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Deprecated:
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#if OPENSSL_API_COMPAT < 0x00908000L
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DH *DH_generate_parameters(int prime_len, int generator,
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void (*callback)(int, int, void *), void *cb_arg);
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#endif
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=head1 DESCRIPTION
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DH_generate_parameters_ex() generates Diffie-Hellman parameters that can
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be shared among a group of users, and stores them in the provided B<DH>
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structure. The pseudo-random number generator must be
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seeded prior to calling DH_generate_parameters().
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B<prime_len> is the length in bits of the safe prime to be generated.
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B<generator> is a small number E<gt> 1, typically 2 or 5.
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A callback function may be used to provide feedback about the progress
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of the key generation. If B<cb> is not B<NULL>, it will be
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called as described in L<BN_generate_prime(3)> while a random prime
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number is generated, and when a prime has been found, B<BN_GENCB_call(cb, 3, 0)>
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is called. See L<BN_generate_prime(3)> for information on
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the BN_GENCB_call() function.
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DH_check_params() confirms that the B<p> and B<g> are likely enough to
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be valid.
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This is a lightweight check, if a more thorough check is needed, use
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DH_check().
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The value of B<*codes> is updated with any problems found.
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If B<*codes> is zero then no problems were found, otherwise the
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following bits may be set:
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=over 4
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=item DH_CHECK_P_NOT_PRIME
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The parameter B<p> has been determined to not being an odd prime.
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Note that the lack of this bit doesn't guarantee that B<p> is a
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prime.
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=item DH_NOT_SUITABLE_GENERATOR
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The generator B<g> is not suitable.
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Note that the lack of this bit doesn't guarantee that B<g> is
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suitable, unless B<p> is known to be a strong prime.
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=back
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DH_check() confirms that the Diffie-Hellman parameters B<dh> are valid. The
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value of B<*codes> is updated with any problems found. If B<*codes> is zero then
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no problems were found, otherwise the following bits may be set:
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=over 4
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=item DH_CHECK_P_NOT_PRIME
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The parameter B<p> is not prime.
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=item DH_CHECK_P_NOT_SAFE_PRIME
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The parameter B<p> is not a safe prime and no B<q> value is present.
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=item DH_UNABLE_TO_CHECK_GENERATOR
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The generator B<g> cannot be checked for suitability.
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=item DH_NOT_SUITABLE_GENERATOR
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The generator B<g> is not suitable.
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=item DH_CHECK_Q_NOT_PRIME
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The parameter B<q> is not prime.
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=item DH_CHECK_INVALID_Q_VALUE
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The parameter B<q> is invalid.
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=item DH_CHECK_INVALID_J_VALUE
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The parameter B<j> is invalid.
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=back
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=head1 RETURN VALUES
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DH_generate_parameters_ex(), DH_check() and DH_check_params() return 1
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if the check could be performed, 0 otherwise.
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DH_generate_parameters() (deprecated) returns a pointer to the DH structure, or
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NULL if the parameter generation fails.
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The error codes can be obtained by L<ERR_get_error(3)>.
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=head1 NOTES
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DH_generate_parameters_ex() and DH_generate_parameters() may run for several
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hours before finding a suitable prime.
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The parameters generated by DH_generate_parameters_ex() and DH_generate_parameters()
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are not to be used in signature schemes.
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=head1 SEE ALSO
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L<DH_new(3)>, L<ERR_get_error(3)>, L<RAND_bytes(3)>,
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L<DH_free(3)>
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=head1 COPYRIGHT
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Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (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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