mirror of https://github.com/openssl/openssl.git
121 lines
3.7 KiB
Plaintext
121 lines
3.7 KiB
Plaintext
=pod
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=head1 NAME
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DSA_generate_parameters_ex, DSA_generate_parameters - generate DSA parameters
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=head1 SYNOPSIS
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#include <openssl/dsa.h>
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int DSA_generate_parameters_ex(DSA *dsa, int bits,
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const unsigned char *seed,int seed_len,
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int *counter_ret, unsigned long *h_ret, BN_GENCB *cb);
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Deprecated:
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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_ex() generates primes p and q and a generator g
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for use in the DSA and stores the result in B<dsa>.
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B<bits> is the length of the prime p to be generated.
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For lengths under 2048 bits, the length of q is 160 bits; for lengths
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greater than or equal to 2048 bits, the length of q is set to 256 bits.
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If B<seed> is NULL, the primes will be generated at random.
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If B<seed_len> is less than the length of q, an error is returned.
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DSA_generate_parameters_ex() 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<cb> is not B<NULL>, it will be
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called as shown below. For information on the BN_GENCB structure and the
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BN_GENCB_call function discussed below, refer to
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L<BN_generate_prime(3)>.
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=over 4
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=item *
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When a candidate for q is generated, B<BN_GENCB_call(cb, 0, m++)> 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<BN_GENCB_call(cb, 1, -1)> is called.
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While a candidate for q is tested by Miller-Rabin primality tests,
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B<BN_GENCB_call(cb, 1, i)> 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<BN_GENCB_call(cb, 2, 0)> and
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B<BN_GENCB_call(cb, 3, 0)> 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<BN_GENCB_call(cb, 0, counter)> 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<BN_GENCB_call(cb, 1, -1)> is called.
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While it is tested by the Miller-Rabin primality test,
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B<BN_GENCB_call(cb, 1, i)> 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<BN_GENCB_call(cb, 2, 1)> is called.
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=item *
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When the generator has been found, B<BN_GENCB_call(cb, 3, 1)> is called.
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=back
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DSA_generate_parameters() (deprecated) works in much the same way as for DSA_generate_parameters_ex, except that no B<dsa> parameter is passed and
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instead a newly allocated B<DSA> structure is returned. Additionally "old
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style" callbacks are used instead of the newer BN_GENCB based approach.
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Refer to L<BN_generate_prime(3)> for further information.
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=head1 RETURN VALUE
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DSA_generate_parameters_ex() returns a 1 on success, or 0 otherwise.
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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.
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The error codes can be obtained by L<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)>, L<ERR_get_error(3)>, L<rand(3)>,
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L<DSA_free(3)>, L<BN_generate_prime(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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