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.
RETURN VALUES
The functions return 1 on success, 0 on error. The error codes can be obtained by ERR_get_error(3).
SEE ALSO
HISTORY
BN_rand() first appeared in SSLeay 0.5.1
and has been available since OpenBSD 2.4.
BN_pseudo_rand() first appeared in OpenSSL
0.9.5 and has been available since OpenBSD 2.7.
The top == -1 case and the function
BN_rand_range() first appeared in OpenSSL 0.9.6a and
have been available since OpenBSD 3.0.
BN_pseudo_rand_range() first appeared in
OpenSSL 0.9.6c and have been available since OpenBSD
3.2.