83 lines
2.6 KiB
Plaintext
83 lines
2.6 KiB
Plaintext
=pod
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=head1 NAME
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DH_generate_parameters_ex, DH_generate_parameters,
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DH_check - generate and check Diffie-Hellman 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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Deprecated:
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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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=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)|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)|BN_generate_prime(3)> for information on
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the BN_GENCB_call() function.
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DH_check() validates Diffie-Hellman parameters. It checks that B<p> is
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a safe prime, and that B<g> is a suitable generator. In the case of an
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error, the bit flags DH_CHECK_P_NOT_SAFE_PRIME or
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DH_NOT_SUITABLE_GENERATOR are set in B<*codes>.
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DH_UNABLE_TO_CHECK_GENERATOR is set if the generator cannot be
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checked, i.e. it does not equal 2 or 5.
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=head1 RETURN VALUES
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DH_generate_parameters_ex() and DH_check() return 1 if the check could be
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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)|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 BUGS
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If B<generator> is not 2 or 5, B<dh-E<gt>g>=B<generator> is not
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a usable generator.
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=head1 SEE ALSO
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L<dh(3)|dh(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>,
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L<DH_free(3)|DH_free(3)>
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=head1 HISTORY
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DH_check() is available in all versions of SSLeay and OpenSSL.
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The B<cb_arg> argument to DH_generate_parameters() was added in SSLeay 0.9.0.
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In versions before OpenSSL 0.9.5, DH_CHECK_P_NOT_STRONG_PRIME is used
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instead of DH_CHECK_P_NOT_SAFE_PRIME.
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=cut
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