1DSA_generate_parameters(3)          OpenSSL         DSA_generate_parameters(3)
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NAME

6       DSA_generate_parameters - generate DSA parameters
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SYNOPSIS

9        #include <openssl/dsa.h>
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11        DSA *DSA_generate_parameters(int bits, unsigned char *seed,
12                       int seed_len, int *counter_ret, unsigned long *h_ret,
13                       void (*callback)(int, int, void *), void *cb_arg);
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DESCRIPTION

16       DSA_generate_parameters() generates primes p and q and a generator g
17       for use in the DSA.
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19       bits is the length of the prime to be generated; the DSS allows a maxi‐
20       mum of 1024 bits.
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22       If seed is NULL or seed_len < 20, the primes will be generated at ran‐
23       dom. Otherwise, the seed is used to generate them. If the given seed
24       does not yield a prime q, a new random seed is chosen and placed at
25       seed.
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27       DSA_generate_parameters() places the iteration count in *counter_ret
28       and a counter used for finding a generator in *h_ret, unless these are
29       NULL.
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31       A callback function may be used to provide feedback about the progress
32       of the key generation. If callback is not NULL, it will be called as
33       follows:
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35       ·   When a candidate for q is generated, callback(0, m++, cb_arg) is
36           called (m is 0 for the first candidate).
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38       ·   When a candidate for q has passed a test by trial division, call‐
39           back(1, -1, cb_arg) is called.  While a candidate for q is tested
40           by Miller-Rabin primality tests, callback(1, i, cb_arg) is called
41           in the outer loop (once for each witness that confirms that the
42           candidate may be prime); i is the loop counter (starting at 0).
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44       ·   When a prime q has been found, callback(2, 0, cb_arg) and call‐
45           back(3, 0, cb_arg) are called.
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47       ·   Before a candidate for p (other than the first) is generated and
48           tested, callback(0, counter, cb_arg) is called.
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50       ·   When a candidate for p has passed the test by trial division, call‐
51           back(1, -1, cb_arg) is called.  While it is tested by the Miller-
52           Rabin primality test, callback(1, i, cb_arg) is called in the outer
53           loop (once for each witness that confirms that the candidate may be
54           prime).  i is the loop counter (starting at 0).
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56       ·   When p has been found, callback(2, 1, cb_arg) is called.
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58       ·   When the generator has been found, callback(3, 1, cb_arg) is
59           called.
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RETURN VALUE

62       DSA_generate_parameters() returns a pointer to the DSA structure, or
63       NULL if the parameter generation fails. The error codes can be obtained
64       by ERR_get_error(3).
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BUGS

67       Seed lengths > 20 are not supported.
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SEE ALSO

70       dsa(3), ERR_get_error(3), rand(3), DSA_free(3)
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HISTORY

73       DSA_generate_parameters() appeared in SSLeay 0.8. The cb_arg argument
74       was added in SSLeay 0.9.0.  In versions up to OpenSSL 0.9.4, call‐
75       back(1, ...) was called in the inner loop of the Miller-Rabin test
76       whenever it reached the squaring step (the parameters to callback did
77       not reveal how many witnesses had been tested); since OpenSSL 0.9.5,
78       callback(1, ...)  is called as in BN_is_prime(3), i.e. once for each
79       witness.  =cut
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830.9.8b                            2002-09-25        DSA_generate_parameters(3)
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