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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.

1.0.1e				  2013-02-11			   RAND_add(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | SEE ALSO | HISTORY

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