/usr/man/cat.3/RAND_get_rand_method.3

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.

1.0.2t               Last change: 2019-09-10                    1

RAND_set_rand_method(3)      OpenSSL      RAND_set_rand_method(3)

     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               Last change: 2019-09-10                    2

See also RAND_SSLeay(3)
See also RAND_set_rand_method(3)