openssl/doc/man3/RAND_bytes.pod

=pod

=head1 NAME

RAND_bytes, RAND_priv_bytes, RAND_pseudo_bytes - generate random data

=head1 SYNOPSIS

 #include <openssl/rand.h>

 int RAND_bytes(unsigned char *buf, int num);
 int RAND_priv_bytes(unsigned char *buf, int num);

Deprecated since OpenSSL 1.1.0, can be hidden entirely by defining
B<OPENSSL_API_COMPAT> with a suitable version value, see
L<openssl_user_macros(7)>:

 int RAND_pseudo_bytes(unsigned char *buf, int num);

=head1 DESCRIPTION

RAND_bytes() puts B<num> cryptographically strong pseudo-random bytes
into B<buf>.

RAND_priv_bytes() has the same semantics as RAND_bytes().  It is intended to
be used for generating values that should remain private. If using the
default RAND_METHOD, this function uses a separate "private" PRNG
instance so that a compromise of the "public" PRNG instance will not
affect the secrecy of these private values, as described in L<RAND(7)>
and L<RAND_DRBG(7)>.

=head1 NOTES

Always check the error return value of RAND_bytes() and
RAND_priv_bytes() and do not take randomness for granted: an error occurs
if the CSPRNG has not been seeded with enough randomness to ensure an
unpredictable byte sequence.

=head1 RETURN VALUES

RAND_bytes() and RAND_priv_bytes()
return 1 on success, -1 if not supported by the current
RAND method, or 0 on other failure. The error code can be
obtained by L<ERR_get_error(3)>.

=head1 HISTORY

=over 2

=item *

RAND_pseudo_bytes() was deprecated in OpenSSL 1.1.0; use RAND_bytes() instead.

=item *

RAND_priv_bytes() was added in OpenSSL 1.1.1.

=back

=head1 SEE ALSO

L<RAND_add(3)>,
L<RAND_bytes(3)>,
L<RAND_priv_bytes(3)>,
L<ERR_get_error(3)>,
L<RAND(7)>,
L<RAND_DRBG(7)>

=head1 COPYRIGHT

Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.

=cut