Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / RAND_set_rand_method.3
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124.\" ========================================================================
125.\"
126.IX Title "RAND_set_rand_method 3"
e3261593 127.TH RAND_set_rand_method 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"
74dab6c2 133RAND_set_rand_method, RAND_get_rand_method, RAND_SSLeay \- select RAND method
984263bc 134.SH "SYNOPSIS"
8b0cefbb 135.IX Header "SYNOPSIS"
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136.Vb 1
137\& #include <openssl/rand.h>
e257b235 138\&
984263bc 139\& void RAND_set_rand_method(const RAND_METHOD *meth);
e257b235 140\&
984263bc 141\& const RAND_METHOD *RAND_get_rand_method(void);
e257b235 142\&
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143\& RAND_METHOD *RAND_SSLeay(void);
144.Ve
145.SH "DESCRIPTION"
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146.IX Header "DESCRIPTION"
147A \fB\s-1RAND_METHOD\s0\fR specifies the functions that OpenSSL uses for random number
984263bc 148generation. By modifying the method, alternative implementations such as
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149hardware RNGs may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for important
150information 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.
984263bc 152.PP
8b0cefbb 153Initially, the default \s-1RAND_METHOD\s0 is the OpenSSL internal implementation, as
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154returned by \fIRAND_SSLeay()\fR.
155.PP
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156\&\fIRAND_set_default_method()\fR makes \fBmeth\fR the method for \s-1PRNG\s0 use. \fB\s-1NB\s0\fR: This is
157true only whilst no \s-1ENGINE\s0 has been set as a default for \s-1RAND\s0, so this function
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158is no longer recommended.
159.PP
8b0cefbb 160\&\fIRAND_get_default_method()\fR returns a pointer to the current \s-1RAND_METHOD\s0.
aac4ff6f 161However, the meaningfulness of this result is dependent on whether the \s-1ENGINE\s0
8b0cefbb 162\&\s-1API\s0 is being used, so this function is no longer recommended.
984263bc 163.SH "THE RAND_METHOD STRUCTURE"
8b0cefbb 164.IX Header "THE RAND_METHOD STRUCTURE"
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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
8b0cefbb 176.PP
984263bc 177The components point to the implementation of \fIRAND_seed()\fR,
8b0cefbb 178\&\fIRAND_bytes()\fR, \fIRAND_cleanup()\fR, \fIRAND_add()\fR, \fIRAND_pseudo_rand()\fR
984263bc 179and \fIRAND_status()\fR.
8b0cefbb 180Each component may be \s-1NULL\s0 if the function is not implemented.
984263bc 181.SH "RETURN VALUES"
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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.
984263bc 185.SH "NOTES"
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186.IX Header "NOTES"
187As of version 0.9.7, \s-1RAND_METHOD\s0 implementations are grouped together with other
188algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \fB\s-1ENGINE\s0\fR modules. If a
189default \s-1ENGINE\s0 is specified for \s-1RAND\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function,
190that 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
192to control default implementations for use in \s-1RAND\s0 and other cryptographic
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193algorithms.
194.SH "SEE ALSO"
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195.IX Header "SEE ALSO"
196\&\fIrand\fR\|(3), \fIengine\fR\|(3)
984263bc 197.SH "HISTORY"
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198.IX Header "HISTORY"
199\&\fIRAND_set_rand_method()\fR, \fIRAND_get_rand_method()\fR and \fIRAND_SSLeay()\fR are
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200available in all versions of OpenSSL.
201.PP
202In the engine version of version 0.9.6, \fIRAND_set_rand_method()\fR was altered to
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203take an \s-1ENGINE\s0 pointer as its argument. As of version 0.9.7, that has been
204reverted as the \s-1ENGINE\s0 \s-1API\s0 transparently overrides \s-1RAND\s0 defaults if used,
205otherwise \s-1RAND\s0 \s-1API\s0 functions work as before. \fIRAND_set_rand_engine()\fR was also
984263bc 206introduced in version 0.9.7.