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RAND_set_rand_method(3)                            OpenSSL                           RAND_set_rand_method(3)



NAME
       RAND_set_rand_method, RAND_get_rand_method, RAND_SSLeay - select RAND method

SYNOPSIS
        #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
       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 dependent on whether the ENGINE API is being used, so this function is no longer
       recommended.

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

NOTES
       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
       rand(3), engine(3)

HISTORY
       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.



50                                               2013-03-05                          RAND_set_rand_method(3)