NAME    [Toc]    [Back]

       BN_rand, BN_pseudo_rand - generate pseudo-random number

LIBRARY    [Toc]    [Back]

       libcrypto, -lcrypto

SYNOPSIS    [Toc]    [Back]

        #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    [Toc]    [Back]

       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    [Toc]    [Back]

       The functions return 1 on success, 0 on error.  The error
       codes can be obtained by ERR_get_error(3).

SEE ALSO    [Toc]    [Back]

       openssl_bn(3), openssl_err(3), openssl_rand(3),
       RAND_add(3), RAND_bytes(3)

HISTORY    [Toc]    [Back]

       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.



2002-07-31                    0.9.6g                   BN_rand(3)