/usr/man2/cat.3/RAND_set_rand_method.3.Z(/usr/man2/cat.3/RAND_set_rand_method.3.Z)

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 num-
       ber 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 implementa-
       tion, 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.

1.0.2t                            2019-09-10           RAND_set_rand_method(3)
See also RAND_SSLeay(3)
See also RAND_get_rand_method(3)