SIMPLE SOLUTIONS

BN_RAND, BN_PSEUDO_RAND, … - reference manual online

Generate pseudo-random number.

Chapter
2016-03-01
```BN_rand(3SSL)                                OpenSSL                                BN_rand(3SSL)

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);

DESCRIPTION
BN_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. The value of bits must be zero or
greater. If bits is 1 then top cannot also be 1.

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 <= 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).

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.

1.0.2g                                      2016-03-01                              BN_rand(3SSL)```
 This manual Reference Other manuals BN_rand(3ssl) referred by bn(3ssl) | rand(3ssl) refer to bn(3ssl) | ERR_get_error(3ssl) | rand(3) | RAND_add(3ssl) | RAND_bytes(3ssl)