/usr/man/cat.3/BN_rand.3

BN_rand(3)                   OpenSSL                   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);

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

1.0.2t               Last change: 2019-09-10                    1

BN_rand(3)                   OpenSSL                   BN_rand(3)

     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.

1.0.2t               Last change: 2019-09-10                    2

See also BN_pseudo_rand(3)
See also BN_pseudo_rand_range(3)
See also BN_rand_range(3)