BN_rand(3)BN_rand(3)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
The BN_rand() function generates a cryptographically strong pseudo-ran‐
dom number of 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 num‐
ber 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.
The BN_pseudo_rand() function 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.
The BN_rand_range() function 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 unpredictible.
The PRNG must be seeded prior to calling the BN_rand() or
BN_rand_range() functions.
RETURN VALUES
The functions return 1 on success, 0 on error. The error codes can be
obtained by using ERR_get_error().
HISTORY
The BN_rand() function is available in all versions of SSLeay and
OpenSSL. The BN_pseudo_rand() function was added in OpenSSL 0.9.5. The
top == -1 case and the BN_rand_range() function were added in OpenSSL
0.9.6a. BN_pseudo_rand_range() was added in OpenSSL 0.9.6c.
SEE ALSO
Functions: bn(3), err(3), rand_ssl(3), RAND_add(3), RAND_bytes(3)BN_rand(3)