freebsd-skq/secure/lib/libcrypto/man/RAND_bytes.3
2006-07-29 19:41:41 +00:00

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.\" ========================================================================
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.IX Title "RAND_bytes 3"
.TH RAND_bytes 3 "2006-07-29" "0.9.8b" "OpenSSL"
.SH "NAME"
RAND_bytes, RAND_pseudo_bytes \- generate random data
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/rand.h>
.Ve
.PP
.Vb 1
\& int RAND_bytes(unsigned char *buf, int num);
.Ve
.PP
.Vb 1
\& int RAND_pseudo_bytes(unsigned char *buf, int num);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fIRAND_bytes()\fR puts \fBnum\fR cryptographically strong pseudo-random bytes
into \fBbuf\fR. An error occurs if the \s-1PRNG\s0 has not been seeded with
enough randomness to ensure an unpredictable byte sequence.
.PP
\&\fIRAND_pseudo_bytes()\fR puts \fBnum\fR pseudo-random bytes into \fBbuf\fR.
Pseudo-random byte sequences generated by \fIRAND_pseudo_bytes()\fR will be
unique if they are of sufficient length, but are not necessarily
unpredictable. They can be used for non-cryptographic purposes and for
certain purposes in cryptographic protocols, but usually not for key
generation etc.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIRAND_bytes()\fR returns 1 on success, 0 otherwise. The error code can be
obtained by \fIERR_get_error\fR\|(3). \fIRAND_pseudo_bytes()\fR returns 1 if the
bytes generated are cryptographically strong, 0 otherwise. Both
functions return \-1 if they are not supported by the current \s-1RAND\s0
method.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIrand\fR\|(3), \fIERR_get_error\fR\|(3),
\&\fIRAND_add\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fIRAND_bytes()\fR is available in all versions of SSLeay and OpenSSL. It
has a return value since OpenSSL 0.9.5. \fIRAND_pseudo_bytes()\fR was added
in OpenSSL 0.9.5.