Update build for OpenSSL-0.9.8j upgrade.
[dragonfly.git] / secure / lib / libcrypto / man / DH_generate_parameters.3
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132.\" ========================================================================
133.\"
134.IX Title "DH_generate_parameters 3"
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135.TH DH_generate_parameters 3 "2009-01-11" "0.9.8j" "OpenSSL"
136.\" For nroff, turn off justification. Always turn off hyphenation; it makes
137.\" way too many mistakes in technical documents.
138.if n .ad l
139.nh
984263bc 140.SH "NAME"
8b0cefbb 141DH_generate_parameters, DH_check \- generate and check Diffie\-Hellman parameters
984263bc 142.SH "SYNOPSIS"
8b0cefbb 143.IX Header "SYNOPSIS"
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144.Vb 1
145\& #include <openssl/dh.h>
e257b235 146\&
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147\& DH *DH_generate_parameters(int prime_len, int generator,
148\& void (*callback)(int, int, void *), void *cb_arg);
e257b235 149\&
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150\& int DH_check(DH *dh, int *codes);
151.Ve
152.SH "DESCRIPTION"
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153.IX Header "DESCRIPTION"
154\&\fIDH_generate_parameters()\fR generates Diffie-Hellman parameters that can
984263bc 155be shared among a group of users, and returns them in a newly
8b0cefbb 156allocated \fB\s-1DH\s0\fR structure. The pseudo-random number generator must be
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157seeded prior to calling \fIDH_generate_parameters()\fR.
158.PP
8b0cefbb 159\&\fBprime_len\fR is the length in bits of the safe prime to be generated.
e257b235 160\&\fBgenerator\fR is a small number > 1, typically 2 or 5.
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161.PP
162A callback function may be used to provide feedback about the progress
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163of the key generation. If \fBcallback\fR is not \fB\s-1NULL\s0\fR, it will be
164called as described in \fIBN_generate_prime\fR\|(3) while a random prime
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165number is generated, and when a prime has been found, \fBcallback(3,
1660, cb_arg)\fR is called.
167.PP
8b0cefbb 168\&\fIDH_check()\fR validates Diffie-Hellman parameters. It checks that \fBp\fR is
984263bc 169a safe prime, and that \fBg\fR is a suitable generator. In the case of an
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170error, the bit flags \s-1DH_CHECK_P_NOT_SAFE_PRIME\s0 or
171\&\s-1DH_NOT_SUITABLE_GENERATOR\s0 are set in \fB*codes\fR.
172\&\s-1DH_UNABLE_TO_CHECK_GENERATOR\s0 is set if the generator cannot be
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173checked, i.e. it does not equal 2 or 5.
174.SH "RETURN VALUES"
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175.IX Header "RETURN VALUES"
176\&\fIDH_generate_parameters()\fR returns a pointer to the \s-1DH\s0 structure, or
177\&\s-1NULL\s0 if the parameter generation fails. The error codes can be
178obtained by \fIERR_get_error\fR\|(3).
984263bc 179.PP
8b0cefbb 180\&\fIDH_check()\fR returns 1 if the check could be performed, 0 otherwise.
984263bc 181.SH "NOTES"
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182.IX Header "NOTES"
183\&\fIDH_generate_parameters()\fR may run for several hours before finding a
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184suitable prime.
185.PP
186The parameters generated by \fIDH_generate_parameters()\fR are not to be
187used in signature schemes.
188.SH "BUGS"
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189.IX Header "BUGS"
190If \fBgenerator\fR is not 2 or 5, \fBdh\->g\fR=\fBgenerator\fR is not
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191a usable generator.
192.SH "SEE ALSO"
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193.IX Header "SEE ALSO"
194\&\fIdh\fR\|(3), \fIERR_get_error\fR\|(3), \fIrand\fR\|(3),
195\&\fIDH_free\fR\|(3)
984263bc 196.SH "HISTORY"
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197.IX Header "HISTORY"
198\&\fIDH_check()\fR is available in all versions of SSLeay and OpenSSL.
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199The \fBcb_arg\fR argument to \fIDH_generate_parameters()\fR was added in SSLeay 0.9.0.
200.PP
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201In versions before OpenSSL 0.9.5, \s-1DH_CHECK_P_NOT_STRONG_PRIME\s0 is used
202instead of \s-1DH_CHECK_P_NOT_SAFE_PRIME\s0.