openssl/doc/crypto/BN_rand.pod
Richard Levitte 6859cf7459 It makes more sense to refer to specific function manuals than the concept
manual when the specific function is refered to in the current manual text.
This correction was originally introduced in OpenBSD's tracking of OpenSSL.
2002-09-25 13:33:28 +00:00

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=pod
=head1 NAME
BN_rand, BN_pseudo_rand - generate pseudo-random number
=head1 SYNOPSIS
#include <openssl/bn.h>
int BN_rand(BIGNUM *rnd, int bits, int top, int bottom);
int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom);
int BN_rand_range(BIGNUM *rnd, BIGNUM *range);
int BN_pseudo_rand_range(BIGNUM *rnd, BIGNUM *range);
=head1 DESCRIPTION
BN_rand() generates a cryptographically strong pseudo-random number of
B<bits> bits in length and stores it in B<rnd>. If B<top> is -1, the
most significant bit of the random number can be zero. If B<top> is 0,
it is set to 1, and if B<top> is 1, the two most significant bits of
the number will be set to 1, so that the product of two such random
numbers will always have 2*B<bits> length. If B<bottom> is true, the
number will be odd.
BN_pseudo_rand() does the same, but pseudo-random numbers generated by
this function 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.
BN_rand_range() generates a cryptographically strong pseudo-random
number B<rnd> in the range 0 <lt>= B<rnd> E<lt> B<range>.
BN_pseudo_rand_range() does the same, but is based on BN_pseudo_rand(),
and hence numbers generated by it are not necessarily unpredictable.
The PRNG must be seeded prior to calling BN_rand() or BN_rand_range().
=head1 RETURN VALUES
The functions return 1 on success, 0 on error.
The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
=head1 SEE ALSO
L<bn(3)|bn(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>,
L<RAND_add(3)|RAND_add(3)>, L<RAND_bytes(3)|RAND_bytes(3)>
=head1 HISTORY
BN_rand() is available in all versions of SSLeay and OpenSSL.
BN_pseudo_rand() was added in OpenSSL 0.9.5. The B<top> == -1 case
and the function BN_rand_range() were added in OpenSSL 0.9.6a.
BN_pseudo_rand_range() was added in OpenSSL 0.9.6c.
=cut