BN_RAND(3) BSD Library Functions Manual BN_RAND(3)NAME
BN_rand, BN_pseudo_rand, BN_rand_range, BN_pseudo_rand_range — 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);
DESCRIPTIONBN_rand() generates a cryptographically strong pseudo-random 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 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 pro‐
tocols, but usually not for key generation etc.
BN_rand_range() generates a cryptographically strong pseudo-random number
rnd in the range 0 <= 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.
RETURN VALUES
The functions return 1 on success, 0 on error. The error codes can be
obtained by ERR_get_error(3).
SEE ALSObn(3), ERR_get_error(3), rand(3), RAND_add(3), RAND_bytes(3)HISTORYBN_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.
BSD May 15, 2024 BSD