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BN_rand(3)                          OpenSSL                         BN_rand(3)



NAME
       BN_rand, BN_pseudo_rand - generate pseudo-random number

LIBRARY
       libcrypto, -lcrypto

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.

       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
       openssl_bn(3), ERR_get_error(3), openssl_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.



1.0.1u                            2016-03-10                        BN_rand(3)