Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / DH_generate_parameters.3
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124.\" ========================================================================
125.\"
126.IX Title "DH_generate_parameters 3"
e3261593 127.TH DH_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"
8b0cefbb 133DH_generate_parameters, DH_check \- generate and check Diffie\-Hellman parameters
984263bc 134.SH "SYNOPSIS"
8b0cefbb 135.IX Header "SYNOPSIS"
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136.Vb 1
137\& #include <openssl/dh.h>
e257b235 138\&
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139\& DH *DH_generate_parameters(int prime_len, int generator,
140\& void (*callback)(int, int, void *), void *cb_arg);
e257b235 141\&
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142\& int DH_check(DH *dh, int *codes);
143.Ve
144.SH "DESCRIPTION"
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145.IX Header "DESCRIPTION"
146\&\fIDH_generate_parameters()\fR generates Diffie-Hellman parameters that can
984263bc 147be shared among a group of users, and returns them in a newly
8b0cefbb 148allocated \fB\s-1DH\s0\fR structure. The pseudo-random number generator must be
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149seeded prior to calling \fIDH_generate_parameters()\fR.
150.PP
8b0cefbb 151\&\fBprime_len\fR is the length in bits of the safe prime to be generated.
e257b235 152\&\fBgenerator\fR is a small number > 1, typically 2 or 5.
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153.PP
154A callback function may be used to provide feedback about the progress
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155of the key generation. If \fBcallback\fR is not \fB\s-1NULL\s0\fR, it will be
156called as described in \fIBN_generate_prime\fR\|(3) while a random prime
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157number is generated, and when a prime has been found, \fBcallback(3,
1580, cb_arg)\fR is called.
159.PP
8b0cefbb 160\&\fIDH_check()\fR validates Diffie-Hellman parameters. It checks that \fBp\fR is
984263bc 161a safe prime, and that \fBg\fR is a suitable generator. In the case of an
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162error, the bit flags \s-1DH_CHECK_P_NOT_SAFE_PRIME\s0 or
163\&\s-1DH_NOT_SUITABLE_GENERATOR\s0 are set in \fB*codes\fR.
164\&\s-1DH_UNABLE_TO_CHECK_GENERATOR\s0 is set if the generator cannot be
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165checked, i.e. it does not equal 2 or 5.
166.SH "RETURN VALUES"
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167.IX Header "RETURN VALUES"
168\&\fIDH_generate_parameters()\fR returns a pointer to the \s-1DH\s0 structure, or
169\&\s-1NULL\s0 if the parameter generation fails. The error codes can be
170obtained by \fIERR_get_error\fR\|(3).
984263bc 171.PP
8b0cefbb 172\&\fIDH_check()\fR returns 1 if the check could be performed, 0 otherwise.
984263bc 173.SH "NOTES"
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174.IX Header "NOTES"
175\&\fIDH_generate_parameters()\fR may run for several hours before finding a
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176suitable prime.
177.PP
178The parameters generated by \fIDH_generate_parameters()\fR are not to be
179used in signature schemes.
180.SH "BUGS"
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181.IX Header "BUGS"
182If \fBgenerator\fR is not 2 or 5, \fBdh\->g\fR=\fBgenerator\fR is not
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183a usable generator.
184.SH "SEE ALSO"
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185.IX Header "SEE ALSO"
186\&\fIdh\fR\|(3), \fIERR_get_error\fR\|(3), \fIrand\fR\|(3),
187\&\fIDH_free\fR\|(3)
984263bc 188.SH "HISTORY"
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189.IX Header "HISTORY"
190\&\fIDH_check()\fR is available in all versions of SSLeay and OpenSSL.
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191The \fBcb_arg\fR argument to \fIDH_generate_parameters()\fR was added in SSLeay 0.9.0.
192.PP
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193In versions before OpenSSL 0.9.5, \s-1DH_CHECK_P_NOT_STRONG_PRIME\s0 is used
194instead of \s-1DH_CHECK_P_NOT_SAFE_PRIME\s0.