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| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "dh 3" |
| 132 | .TH dh 3 "2008-09-06" "0.9.8h" "OpenSSL" |
| 133 | .SH "NAME" |
| 134 | dh \- Diffie\-Hellman key agreement |
| 135 | .SH "SYNOPSIS" |
| 136 | .IX Header "SYNOPSIS" |
| 137 | .Vb 2 |
| 138 | \& #include <openssl/dh.h> |
| 139 | \& #include <openssl/engine.h> |
| 140 | .Ve |
| 141 | .PP |
| 142 | .Vb 2 |
| 143 | \& DH * DH_new(void); |
| 144 | \& void DH_free(DH *dh); |
| 145 | .Ve |
| 146 | .PP |
| 147 | .Vb 1 |
| 148 | \& int DH_size(const DH *dh); |
| 149 | .Ve |
| 150 | .PP |
| 151 | .Vb 3 |
| 152 | \& DH * DH_generate_parameters(int prime_len, int generator, |
| 153 | \& void (*callback)(int, int, void *), void *cb_arg); |
| 154 | \& int DH_check(const DH *dh, int *codes); |
| 155 | .Ve |
| 156 | .PP |
| 157 | .Vb 2 |
| 158 | \& int DH_generate_key(DH *dh); |
| 159 | \& int DH_compute_key(unsigned char *key, BIGNUM *pub_key, DH *dh); |
| 160 | .Ve |
| 161 | .PP |
| 162 | .Vb 5 |
| 163 | \& void DH_set_default_method(const DH_METHOD *meth); |
| 164 | \& const DH_METHOD *DH_get_default_method(void); |
| 165 | \& int DH_set_method(DH *dh, const DH_METHOD *meth); |
| 166 | \& DH *DH_new_method(ENGINE *engine); |
| 167 | \& const DH_METHOD *DH_OpenSSL(void); |
| 168 | .Ve |
| 169 | .PP |
| 170 | .Vb 4 |
| 171 | \& int DH_get_ex_new_index(long argl, char *argp, int (*new_func)(), |
| 172 | \& int (*dup_func)(), void (*free_func)()); |
| 173 | \& int DH_set_ex_data(DH *d, int idx, char *arg); |
| 174 | \& char *DH_get_ex_data(DH *d, int idx); |
| 175 | .Ve |
| 176 | .PP |
| 177 | .Vb 2 |
| 178 | \& DH * d2i_DHparams(DH **a, unsigned char **pp, long length); |
| 179 | \& int i2d_DHparams(const DH *a, unsigned char **pp); |
| 180 | .Ve |
| 181 | .PP |
| 182 | .Vb 2 |
| 183 | \& int DHparams_print_fp(FILE *fp, const DH *x); |
| 184 | \& int DHparams_print(BIO *bp, const DH *x); |
| 185 | .Ve |
| 186 | .SH "DESCRIPTION" |
| 187 | .IX Header "DESCRIPTION" |
| 188 | These functions implement the Diffie-Hellman key agreement protocol. |
| 189 | The generation of shared \s-1DH\s0 parameters is described in |
| 190 | \&\fIDH_generate_parameters\fR\|(3); \fIDH_generate_key\fR\|(3) describes how |
| 191 | to perform a key agreement. |
| 192 | .PP |
| 193 | The \fB\s-1DH\s0\fR structure consists of several \s-1BIGNUM\s0 components. |
| 194 | .PP |
| 195 | .Vb 9 |
| 196 | \& struct |
| 197 | \& { |
| 198 | \& BIGNUM *p; // prime number (shared) |
| 199 | \& BIGNUM *g; // generator of Z_p (shared) |
| 200 | \& BIGNUM *priv_key; // private DH value x |
| 201 | \& BIGNUM *pub_key; // public DH value g^x |
| 202 | \& // ... |
| 203 | \& }; |
| 204 | \& DH |
| 205 | .Ve |
| 206 | .PP |
| 207 | Note that \s-1DH\s0 keys may use non-standard \fB\s-1DH_METHOD\s0\fR implementations, |
| 208 | either directly or by the use of \fB\s-1ENGINE\s0\fR modules. In some cases (eg. an |
| 209 | \&\s-1ENGINE\s0 providing support for hardware-embedded keys), these \s-1BIGNUM\s0 values |
| 210 | will not be used by the implementation or may be used for alternative data |
| 211 | storage. For this reason, applications should generally avoid using \s-1DH\s0 |
| 212 | structure elements directly and instead use \s-1API\s0 functions to query or |
| 213 | modify keys. |
| 214 | .SH "SEE ALSO" |
| 215 | .IX Header "SEE ALSO" |
| 216 | \&\fIdhparam\fR\|(1), \fIbn\fR\|(3), \fIdsa\fR\|(3), \fIerr\fR\|(3), |
| 217 | \&\fIrand\fR\|(3), \fIrsa\fR\|(3), \fIengine\fR\|(3), |
| 218 | \&\fIDH_set_method\fR\|(3), \fIDH_new\fR\|(3), |
| 219 | \&\fIDH_get_ex_new_index\fR\|(3), |
| 220 | \&\fIDH_generate_parameters\fR\|(3), |
| 221 | \&\fIDH_compute_key\fR\|(3), \fId2i_DHparams\fR\|(3), |
| 222 | \&\fIRSA_print\fR\|(3) |