105 lines
3 KiB
Text
105 lines
3 KiB
Text
=pod
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=head1 NAME
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DSA_generate_parameters - generate DSA parameters
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=head1 SYNOPSIS
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#include <openssl/dsa.h>
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DSA *DSA_generate_parameters(int bits, unsigned char *seed,
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int seed_len, int *counter_ret, unsigned long *h_ret,
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void (*callback)(int, int, void *), void *cb_arg);
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=head1 DESCRIPTION
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DSA_generate_parameters() generates primes p and q and a generator g
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for use in the DSA.
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B<bits> is the length of the prime to be generated; the DSS allows a
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maximum of 1024 bits.
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If B<seed> is B<NULL> or B<seed_len> E<lt> 20, the primes will be
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generated at random. Otherwise, the seed is used to generate
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them. If the given seed does not yield a prime q, a new random
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seed is chosen and placed at B<seed>.
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DSA_generate_parameters() places the iteration count in
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*B<counter_ret> and a counter used for finding a generator in
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*B<h_ret>, unless these are B<NULL>.
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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<callback> is not B<NULL>, it will be
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called as follows:
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=over 4
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=item *
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When a candidate for q is generated, B<callback(0, m++, cb_arg)> is called
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(m is 0 for the first candidate).
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=item *
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When a candidate for q has passed a test by trial division,
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B<callback(1, -1, cb_arg)> is called.
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While a candidate for q is tested by Miller-Rabin primality tests,
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B<callback(1, i, cb_arg)> is called in the outer loop
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(once for each witness that confirms that the candidate may be prime);
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i is the loop counter (starting at 0).
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=item *
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When a prime q has been found, B<callback(2, 0, cb_arg)> and
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B<callback(3, 0, cb_arg)> are called.
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=item *
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Before a candidate for p (other than the first) is generated and tested,
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B<callback(0, counter, cb_arg)> is called.
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=item *
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When a candidate for p has passed the test by trial division,
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B<callback(1, -1, cb_arg)> is called.
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While it is tested by the Miller-Rabin primality test,
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B<callback(1, i, cb_arg)> is called in the outer loop
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(once for each witness that confirms that the candidate may be prime).
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i is the loop counter (starting at 0).
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=item *
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When p has been found, B<callback(2, 1, cb_arg)> is called.
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=item *
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When the generator has been found, B<callback(3, 1, cb_arg)> is called.
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=back
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=head1 RETURN VALUE
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DSA_generate_parameters() returns a pointer to the DSA structure, or
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B<NULL> if the parameter generation fails. The error codes can be
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obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
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=head1 BUGS
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Seed lengths E<gt> 20 are not supported.
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=head1 SEE ALSO
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L<dsa(3)|dsa(3)>, L<err(3)|err(3)>, L<rand(3)|rand(3)>,
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L<DSA_free(3)|DSA_free(3)>
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=head1 HISTORY
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DSA_generate_parameters() appeared in SSLeay 0.8. The B<cb_arg>
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argument was added in SSLeay 0.9.0.
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In versions up to OpenSSL 0.9.4, B<callback(1, ...)> was called
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in the inner loop of the Miller-Rabin test whenever it reached the
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squaring step (the parameters to B<callback> did not reveal how many
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witnesses had been tested); since OpenSSL 0.9.5, B<callback(1, ...)>
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is called as in BN_is_prime(3), i.e. once for each witness.
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=cut
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