NAME

       BN_rand, BN_pseudo_rand - 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 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
       protocols, but usually not for key generation etc.

       BN_rand_range() generates a cryptographically strong pseudo-random number rnd in the range 0 <lt>= 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.