openssl/doc/crypto/RAND_bytes.pod

=pod

=head1 NAME

RAND_bytes, RAND_pseudo_bytes - generate random data

=head1 SYNOPSIS

 #include <openssl/rand.h>

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

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

=head1 DESCRIPTION

RAND_bytes() puts B<num> cryptographically strong pseudo-random bytes
into B<buf>. An error occurs if the PRNG has not been seeded with
enough randomness to ensure an unpredictable byte sequence.

RAND_pseudo_bytes() puts B<num> pseudo-random bytes into B<buf>.
Pseudo-random byte sequences generated by RAND_pseudo_bytes() 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.

The contents of B<buf> is mixed into the entropy pool before retrieving
the new pseudo-random bytes unless disabled at compile time (see FAQ).

=head1 RETURN VALUES

RAND_bytes() returns 1 on success, 0 otherwise. The error code can be
obtained by L<ERR_get_error(3)|ERR_get_error(3)>. RAND_pseudo_bytes() returns 1 if the
bytes generated are cryptographically strong, 0 otherwise. Both
functions return -1 if they are not supported by the current RAND
method.

=head1 SEE ALSO

L<rand(3)|rand(3)>, L<ERR_get_error(3)|ERR_get_error(3)>,
L<RAND_add(3)|RAND_add(3)>

=head1 HISTORY

RAND_bytes() is available in all versions of SSLeay and OpenSSL.  It
has a return value since OpenSSL 0.9.5. RAND_pseudo_bytes() was added
in OpenSSL 0.9.5.

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