BN_rand
Section: OpenSSL (3)
Updated: 2017-05-25
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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
bits is less than zero, or too small to
accomodate the requirements specified by the
top and
bottom
parameters, an error is returned.
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).
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.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUES
-
- SEE ALSO
-
- HISTORY
-
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