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124 .\" ========================================================================
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126 .IX Title "RAND_bytes 3"
127 .TH RAND_bytes 3 "2012-01-18" "1.0.0g" "OpenSSL"
128 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
129 .\" way too many mistakes in technical documents.
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132 .SH "NAME"
133 RAND_bytes, RAND_pseudo_bytes \- generate random data
134 .SH "SYNOPSIS"
135 .IX Header "SYNOPSIS"
136 .Vb 1
137 \& #include <openssl/rand.h>
138 \&
139 \& int RAND_bytes(unsigned char *buf, int num);
140 \&
141 \& int RAND_pseudo_bytes(unsigned char *buf, int num);
142 .Ve
143 .SH "DESCRIPTION"
144 .IX Header "DESCRIPTION"
145 \&\fIRAND_bytes()\fR puts \fBnum\fR cryptographically strong pseudo-random bytes
146 into \fBbuf\fR. An error occurs if the \s-1PRNG\s0 has not been seeded with
147 enough randomness to ensure an unpredictable byte sequence.
148 .PP
149 \&\fIRAND_pseudo_bytes()\fR puts \fBnum\fR pseudo-random bytes into \fBbuf\fR.
150 Pseudo-random byte sequences generated by \fIRAND_pseudo_bytes()\fR will be
151 unique if they are of sufficient length, but are not necessarily
152 unpredictable. They can be used for non-cryptographic purposes and for
153 certain purposes in cryptographic protocols, but usually not for key
154 generation etc.
155 .PP
156 The contents of \fBbuf\fR is mixed into the entropy pool before retrieving
157 the new pseudo-random bytes unless disabled at compile time (see \s-1FAQ\s0).
158 .SH "RETURN VALUES"
159 .IX Header "RETURN VALUES"
160 \&\fIRAND_bytes()\fR returns 1 on success, 0 otherwise. The error code can be
161 obtained by \fIERR_get_error\fR\|(3). \fIRAND_pseudo_bytes()\fR returns 1 if the
162 bytes generated are cryptographically strong, 0 otherwise. Both
163 functions return \-1 if they are not supported by the current \s-1RAND\s0
164 method.
165 .SH "SEE ALSO"
166 .IX Header "SEE ALSO"
167 \&\fIrand\fR\|(3), \fIERR_get_error\fR\|(3),
168 \&\fIRAND_add\fR\|(3)
169 .SH "HISTORY"
170 .IX Header "HISTORY"
171 \&\fIRAND_bytes()\fR is available in all versions of SSLeay and OpenSSL. It
172 has a return value since OpenSSL 0.9.5. \fIRAND_pseudo_bytes()\fR was added
173 in OpenSSL 0.9.5.