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RAND(3) 			   LibreSSL			       RAND(3)

NAME
       RAND - pseudo-random number generator

SYNOPSIS
	#include <openssl/rand.h>

	int  RAND_bytes(unsigned char *buf, int num);
	int  RAND_pseudo_bytes(unsigned char *buf, int num);

DESCRIPTION
       These functions give access to the systems cryptographically secure
       pseudo-random number generator (PRNG). It is used by other library
       functions for example to generate random keys, and applications can use
       it when they need randomness.

       RAND_bytes(3) describes how to obtain random data from the PRNG.

INTERNALS
       The RAND_SSLeay() method implements a PRNG based on the systems'
       arc4random_buf(3) random number generator.

SEE ALSO
       BN_rand(3), RAND_bytes(3)

LibreSSL			  2017-01-09			       RAND(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. 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.

1.0.2h                            2016-05-03           RAND_set_rand_method(3)