Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / DSA_generate_parameters.3
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124.\" ========================================================================
125.\"
126.IX Title "DSA_generate_parameters 3"
e3261593 127.TH DSA_generate_parameters 3 "2012-01-04" "1.0.0f" "OpenSSL"
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128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
984263bc 132.SH "NAME"
74dab6c2 133DSA_generate_parameters \- generate DSA parameters
984263bc 134.SH "SYNOPSIS"
8b0cefbb 135.IX Header "SYNOPSIS"
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136.Vb 1
137\& #include <openssl/dsa.h>
e257b235 138\&
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139\& DSA *DSA_generate_parameters(int bits, unsigned char *seed,
140\& int seed_len, int *counter_ret, unsigned long *h_ret,
141\& void (*callback)(int, int, void *), void *cb_arg);
142.Ve
143.SH "DESCRIPTION"
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144.IX Header "DESCRIPTION"
145\&\fIDSA_generate_parameters()\fR generates primes p and q and a generator g
146for use in the \s-1DSA\s0.
984263bc 147.PP
8b0cefbb 148\&\fBbits\fR is the length of the prime to be generated; the \s-1DSS\s0 allows a
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149maximum of 1024 bits.
150.PP
8b0cefbb 151If \fBseed\fR is \fB\s-1NULL\s0\fR or \fBseed_len\fR < 20, the primes will be
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152generated at random. Otherwise, the seed is used to generate
153them. If the given seed does not yield a prime q, a new random
154seed is chosen and placed at \fBseed\fR.
155.PP
8b0cefbb 156\&\fIDSA_generate_parameters()\fR places the iteration count in
984263bc 157*\fBcounter_ret\fR and a counter used for finding a generator in
8b0cefbb 158*\fBh_ret\fR, unless these are \fB\s-1NULL\s0\fR.
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159.PP
160A callback function may be used to provide feedback about the progress
8b0cefbb 161of the key generation. If \fBcallback\fR is not \fB\s-1NULL\s0\fR, it will be
984263bc 162called as follows:
8b0cefbb 163.IP "\(bu" 4
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164When a candidate for q is generated, \fBcallback(0, m++, cb_arg)\fR is called
165(m is 0 for the first candidate).
8b0cefbb 166.IP "\(bu" 4
984263bc 167When a candidate for q has passed a test by trial division,
8b0cefbb 168\&\fBcallback(1, \-1, cb_arg)\fR is called.
984263bc 169While a candidate for q is tested by Miller-Rabin primality tests,
8b0cefbb 170\&\fBcallback(1, i, cb_arg)\fR is called in the outer loop
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171(once for each witness that confirms that the candidate may be prime);
172i is the loop counter (starting at 0).
8b0cefbb 173.IP "\(bu" 4
984263bc 174When a prime q has been found, \fBcallback(2, 0, cb_arg)\fR and
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175\&\fBcallback(3, 0, cb_arg)\fR are called.
176.IP "\(bu" 4
984263bc 177Before a candidate for p (other than the first) is generated and tested,
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178\&\fBcallback(0, counter, cb_arg)\fR is called.
179.IP "\(bu" 4
984263bc 180When a candidate for p has passed the test by trial division,
8b0cefbb 181\&\fBcallback(1, \-1, cb_arg)\fR is called.
984263bc 182While it is tested by the Miller-Rabin primality test,
8b0cefbb 183\&\fBcallback(1, i, cb_arg)\fR is called in the outer loop
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184(once for each witness that confirms that the candidate may be prime).
185i is the loop counter (starting at 0).
8b0cefbb 186.IP "\(bu" 4
984263bc 187When p has been found, \fBcallback(2, 1, cb_arg)\fR is called.
8b0cefbb 188.IP "\(bu" 4
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189When the generator has been found, \fBcallback(3, 1, cb_arg)\fR is called.
190.SH "RETURN VALUE"
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191.IX Header "RETURN VALUE"
192\&\fIDSA_generate_parameters()\fR returns a pointer to the \s-1DSA\s0 structure, or
193\&\fB\s-1NULL\s0\fR if the parameter generation fails. The error codes can be
194obtained by \fIERR_get_error\fR\|(3).
984263bc 195.SH "BUGS"
8b0cefbb 196.IX Header "BUGS"
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197Seed lengths > 20 are not supported.
198.SH "SEE ALSO"
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199.IX Header "SEE ALSO"
200\&\fIdsa\fR\|(3), \fIERR_get_error\fR\|(3), \fIrand\fR\|(3),
201\&\fIDSA_free\fR\|(3)
984263bc 202.SH "HISTORY"
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203.IX Header "HISTORY"
204\&\fIDSA_generate_parameters()\fR appeared in SSLeay 0.8. The \fBcb_arg\fR
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205argument was added in SSLeay 0.9.0.
206In versions up to OpenSSL 0.9.4, \fBcallback(1, ...)\fR was called
207in the inner loop of the Miller-Rabin test whenever it reached the
208squaring step (the parameters to \fBcallback\fR did not reveal how many
209witnesses had been tested); since OpenSSL 0.9.5, \fBcallback(1, ...)\fR
210is called as in \fIBN_is_prime\fR\|(3), i.e. once for each witness.