DragonFly On-Line Manual Pages

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_add(3)                         OpenSSL                        RAND_add(3)

NAME
       RAND_add, RAND_seed, RAND_status, RAND_event, RAND_screen - add entropy
       to the PRNG

SYNOPSIS
        #include <openssl/rand.h>

        void RAND_seed(const void *buf, int num);

        void RAND_add(const void *buf, int num, double entropy);

        int  RAND_status(void);

        int  RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
        void RAND_screen(void);

DESCRIPTION
       RAND_add() mixes the num bytes at buf into the PRNG state. Thus, if the
       data at buf are unpredictable to an adversary, this increases the
       uncertainty about the state and makes the PRNG output less predictable.
       Suitable input comes from user interaction (random key presses, mouse
       movements) and certain hardware events. The entropy argument is (the
       lower bound of) an estimate of how much randomness is contained in buf,
       measured in bytes. Details about sources of randomness and how to
       estimate their entropy can be found in the literature, e.g. RFC 1750.

       RAND_add() may be called with sensitive data such as user entered
       passwords. The seed values cannot be recovered from the PRNG output.

       OpenSSL makes sure that the PRNG state is unique for each thread. On
       systems that provide "/dev/urandom", the randomness device is used to
       seed the PRNG transparently. However, on all other systems, the
       application is responsible for seeding the PRNG by calling RAND_add(),
       RAND_egd(3) or RAND_load_file(3).

       RAND_seed() is equivalent to RAND_add() when num == entropy.

       RAND_event() collects the entropy from Windows events such as mouse
       movements and other user interaction. It should be called with the
       iMsg, wParam and lParam arguments of all messages sent to the window
       procedure. It will estimate the entropy contained in the event message
       (if any), and add it to the PRNG. The program can then process the
       messages as usual.

       The RAND_screen() function is available for the convenience of Windows
       programmers. It adds the current contents of the screen to the PRNG.
       For applications that can catch Windows events, seeding the PRNG by
       calling RAND_event() is a significantly better source of randomness. It
       should be noted that both methods cannot be used on servers that run
       without user interaction.

RETURN VALUES
       RAND_status() and RAND_event() return 1 if the PRNG has been seeded
       with enough data, 0 otherwise.

       The other functions do not return values.

SEE ALSO
       rand(3), RAND_egd(3), RAND_load_file(3), RAND_cleanup(3)

HISTORY
       RAND_seed() and RAND_screen() are available in all versions of SSLeay
       and OpenSSL. RAND_add() and RAND_status() have been added in OpenSSL
       0.9.5, RAND_event() in OpenSSL 0.9.5a.

1.0.2h                            2016-05-03                       RAND_add(3)