NAME
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).
SEE ALSO
bn(3), ERR_get_error(3), rand(3), RAND_add(3), RAND_bytes(3)
HISTORY
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.
