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.