NAME    [Toc]    [Back]

       RAND_set_rand_method, RAND_get_rand_method, RAND_SSLeay -
       select RAND method

SYNOPSIS    [Toc]    [Back]

        #include <openssl/rand.h>

        void RAND_set_rand_method(const RAND_METHOD *meth);

        const RAND_METHOD *RAND_get_rand_method(void);

        RAND_METHOD *RAND_SSLeay(void);

DESCRIPTION    [Toc]    [Back]

       A RAND_METHOD specifies the functions that OpenSSL uses
       for random number generation. By modifying the method,
       alternative implementations such as hardware RNGs may be
       used. IMPORTANT: See the NOTES section for important
       information about how these RAND API functions are
       affected by the use of ENGINE API calls.

       Initially, the default RAND_METHOD is the OpenSSL internal
       implementation, as returned by RAND_SSLeay().

       RAND_set_default_method() makes meth the method for PRNG
       use. NB: This is true only whilst no ENGINE has been set
       as a default for RAND, so this function is no longer recommended.


       RAND_get_default_method() returns a pointer to the current
       RAND_METHOD.  However, the meaningfulness of this result
       is dependant on whether the ENGINE API is being used, so
       this function is no longer recommended.

THE RAND_METHOD STRUCTURE    [Toc]    [Back]

        typedef struct rand_meth_st
        {
               void (*seed)(const void *buf, int num);
               int (*bytes)(unsigned char *buf, int num);
               void (*cleanup)(void);
               void (*add)(const void  *buf,  int  num,  int  entropy);
               int (*pseudorand)(unsigned char *buf, int num);
               int (*status)(void);
        } RAND_METHOD;

       The components point to the implementation of RAND_seed(),
       RAND_bytes(), RAND_cleanup(), RAND_add(),
       RAND_pseudo_rand() and RAND_status().  Each component may
       be NULL if the function is not implemented.

RETURN VALUES    [Toc]    [Back]

       RAND_set_rand_method() returns no value.
       RAND_get_rand_method() and RAND_SSLeay() return pointers
       to the respective methods.

NOTES    [Toc]    [Back]

       As of version 0.9.7, RAND_METHOD implementations are
       grouped together with other algorithmic APIs (eg.
       RSA_METHOD, EVP_CIPHER, etc) in ENGINE modules. If a
       default ENGINE is specified for RAND functionality using
       an ENGINE API function, that will override any RAND
       defaults set using the RAND API (ie.
       RAND_set_rand_method()). For this reason, the ENGINE API
       is the recommended way to control default implementations
       for use in RAND and other cryptographic algorithms.

SEE ALSO    [Toc]    [Back]

       rand(3), engine(3)

HISTORY    [Toc]    [Back]

       RAND_set_rand_method(), RAND_get_rand_method() and
       RAND_SSLeay() are available in all versions of OpenSSL.

       In the engine version of version 0.9.6,
       RAND_set_rand_method() was altered to take an ENGINE
       pointer as its argument. As of version 0.9.7, that has
       been reverted as the ENGINE API transparently overrides
       RAND defaults if used, otherwise RAND API functions work
       as before. RAND_set_rand_engine() was also introduced in
       version 0.9.7.


OpenBSD 3.6                 2002-09-14                          2