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| 124 | .\" ======================================================================== |
| 125 | .\" |
| 126 | .IX Title "RAND_set_rand_method 3" |
| 127 | .TH RAND_set_rand_method 3 "2012-01-04" "1.0.0f" "OpenSSL" |
| 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 |
| 132 | .SH "NAME" |
| 133 | RAND_set_rand_method, RAND_get_rand_method, RAND_SSLeay \- select RAND method |
| 134 | .SH "SYNOPSIS" |
| 135 | .IX Header "SYNOPSIS" |
| 136 | .Vb 1 |
| 137 | \& #include <openssl/rand.h> |
| 138 | \& |
| 139 | \& void RAND_set_rand_method(const RAND_METHOD *meth); |
| 140 | \& |
| 141 | \& const RAND_METHOD *RAND_get_rand_method(void); |
| 142 | \& |
| 143 | \& RAND_METHOD *RAND_SSLeay(void); |
| 144 | .Ve |
| 145 | .SH "DESCRIPTION" |
| 146 | .IX Header "DESCRIPTION" |
| 147 | A \fB\s-1RAND_METHOD\s0\fR specifies the functions that OpenSSL uses for random number |
| 148 | generation. By modifying the method, alternative implementations such as |
| 149 | hardware RNGs may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for important |
| 150 | information about how these \s-1RAND\s0 \s-1API\s0 functions are affected by the use of |
| 151 | \&\fB\s-1ENGINE\s0\fR \s-1API\s0 calls. |
| 152 | .PP |
| 153 | Initially, the default \s-1RAND_METHOD\s0 is the OpenSSL internal implementation, as |
| 154 | returned by \fIRAND_SSLeay()\fR. |
| 155 | .PP |
| 156 | \&\fIRAND_set_default_method()\fR makes \fBmeth\fR the method for \s-1PRNG\s0 use. \fB\s-1NB\s0\fR: This is |
| 157 | true only whilst no \s-1ENGINE\s0 has been set as a default for \s-1RAND\s0, so this function |
| 158 | is no longer recommended. |
| 159 | .PP |
| 160 | \&\fIRAND_get_default_method()\fR returns a pointer to the current \s-1RAND_METHOD\s0. |
| 161 | However, the meaningfulness of this result is dependent on whether the \s-1ENGINE\s0 |
| 162 | \&\s-1API\s0 is being used, so this function is no longer recommended. |
| 163 | .SH "THE RAND_METHOD STRUCTURE" |
| 164 | .IX Header "THE RAND_METHOD STRUCTURE" |
| 165 | .Vb 9 |
| 166 | \& typedef struct rand_meth_st |
| 167 | \& { |
| 168 | \& void (*seed)(const void *buf, int num); |
| 169 | \& int (*bytes)(unsigned char *buf, int num); |
| 170 | \& void (*cleanup)(void); |
| 171 | \& void (*add)(const void *buf, int num, int entropy); |
| 172 | \& int (*pseudorand)(unsigned char *buf, int num); |
| 173 | \& int (*status)(void); |
| 174 | \& } RAND_METHOD; |
| 175 | .Ve |
| 176 | .PP |
| 177 | The components point to the implementation of \fIRAND_seed()\fR, |
| 178 | \&\fIRAND_bytes()\fR, \fIRAND_cleanup()\fR, \fIRAND_add()\fR, \fIRAND_pseudo_rand()\fR |
| 179 | and \fIRAND_status()\fR. |
| 180 | Each component may be \s-1NULL\s0 if the function is not implemented. |
| 181 | .SH "RETURN VALUES" |
| 182 | .IX Header "RETURN VALUES" |
| 183 | \&\fIRAND_set_rand_method()\fR returns no value. \fIRAND_get_rand_method()\fR and |
| 184 | \&\fIRAND_SSLeay()\fR return pointers to the respective methods. |
| 185 | .SH "NOTES" |
| 186 | .IX Header "NOTES" |
| 187 | As of version 0.9.7, \s-1RAND_METHOD\s0 implementations are grouped together with other |
| 188 | algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \fB\s-1ENGINE\s0\fR modules. If a |
| 189 | default \s-1ENGINE\s0 is specified for \s-1RAND\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function, |
| 190 | that will override any \s-1RAND\s0 defaults set using the \s-1RAND\s0 \s-1API\s0 (ie. |
| 191 | \&\fIRAND_set_rand_method()\fR). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the recommended way |
| 192 | to control default implementations for use in \s-1RAND\s0 and other cryptographic |
| 193 | algorithms. |
| 194 | .SH "SEE ALSO" |
| 195 | .IX Header "SEE ALSO" |
| 196 | \&\fIrand\fR\|(3), \fIengine\fR\|(3) |
| 197 | .SH "HISTORY" |
| 198 | .IX Header "HISTORY" |
| 199 | \&\fIRAND_set_rand_method()\fR, \fIRAND_get_rand_method()\fR and \fIRAND_SSLeay()\fR are |
| 200 | available in all versions of OpenSSL. |
| 201 | .PP |
| 202 | In the engine version of version 0.9.6, \fIRAND_set_rand_method()\fR was altered to |
| 203 | take an \s-1ENGINE\s0 pointer as its argument. As of version 0.9.7, that has been |
| 204 | reverted as the \s-1ENGINE\s0 \s-1API\s0 transparently overrides \s-1RAND\s0 defaults if used, |
| 205 | otherwise \s-1RAND\s0 \s-1API\s0 functions work as before. \fIRAND_set_rand_engine()\fR was also |
| 206 | introduced in version 0.9.7. |