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140 .IX Title "DH_generate_key 3"
141 .TH DH_generate_key 3 "0.9.6e" "2000-04-13" "OpenSSL"
144 DH_generate_key, DH_compute_key \- perform Diffie-Hellman key exchange
146 .IX Header "SYNOPSIS"
148 \& #include <openssl/dh.h>
151 \& int DH_generate_key(DH *dh);
154 \& int DH_compute_key(unsigned char *key, BIGNUM *pub_key, DH *dh);
157 .IX Header "DESCRIPTION"
158 \&\fIDH_generate_key()\fR performs the first step of a Diffie-Hellman key
159 exchange by generating private and public \s-1DH\s0 values. By calling
160 \&\fIDH_compute_key()\fR, these are combined with the other party's public
161 value to compute the shared key.
163 \&\fIDH_generate_key()\fR expects \fBdh\fR to contain the shared parameters
164 \&\fBdh->p\fR and \fBdh->g\fR. It generates a random private \s-1DH\s0 value
165 unless \fBdh->priv_key\fR is already set, and computes the
166 corresponding public value \fBdh->pub_key\fR, which can then be
169 \&\fIDH_compute_key()\fR computes the shared secret from the private \s-1DH\s0 value
170 in \fBdh\fR and the other party's public value in \fBpub_key\fR and stores
171 it in \fBkey\fR. \fBkey\fR must point to \fBDH_size(dh)\fR bytes of memory.
173 .IX Header "RETURN VALUES"
174 \&\fIDH_generate_key()\fR returns 1 on success, 0 otherwise.
176 \&\fIDH_compute_key()\fR returns the size of the shared secret on success, \-1
179 The error codes can be obtained by ERR_get_error(3).
181 .IX Header "SEE ALSO"
182 dh(3), err(3), rand(3), DH_size(3)
185 \&\fIDH_generate_key()\fR and \fIDH_compute_key()\fR are available in all versions
186 of SSLeay and OpenSSL.