BN_rand, BN_pseudo_rand -- generate pseudo-random number
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);
DESCRIPTION
BN_rand() generates a cryptographically strong pseudo-random number
of bits bits in length and stores it
in rnd. If top is -1, the most significant bit of the
random number can be zero. If top is
0, it is set to 1, and if 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*bits length. If 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 rnd in the range 0
<lt>= rnd < 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().
RETURN VALUES
The functions return 1 on success, 0 on error. The error codes can be
obtained by ERR_get_error(3).
BN_rand() is available in all versions of SSLeay and OpenSSL.
BN_pseudo_rand() was added in OpenSSL 0.9.5. The 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.
