from small one page howto to huge articles all in one place
 

search text in:





Poll
Which linux distribution do you use?







poll results

Last additions:
using iotop to find disk usage hogs

using iotop to find disk usage hogs

words:

887

views:

101408

userrating:

average rating: 1.7 (84 votes) (1=very good 6=terrible)


May 25th. 2007:
Words

486

Views

216422

why adblockers are bad


Workaround and fixes for the current Core Dump Handling vulnerability affected kernels

Workaround and fixes for the current Core Dump Handling vulnerability affected kernels

words:

161

views:

97264

userrating:

average rating: 1.3 (28 votes) (1=very good 6=terrible)


April, 26th. 2006:

Druckversion
You are here: manpages





RAND_add

Section: OpenSSL (3)
Updated: 2015-01-15
Index Return to Main Contents
 

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.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUES
SEE ALSO
HISTORY


Please read "Why adblockers are bad".



Other free services
toURL.org
Shorten long
URLs to short
links like
http://tourl.org/2
tourl.org
.
Reverse DNS lookup
Find out which hostname(s)
resolve to a
given IP or other hostnames for the server
www.reversednslookup.org
rdf newsfeed | rss newsfeed | Atom newsfeed
- Powered by LeopardCMS - Running on Gentoo -
Copyright 2004-2017 Sascha Nitsch Unternehmensberatung UG(haftungsbeschränkt)
Valid XHTML1.1 : Valid CSS : buttonmaker
- Level Triple-A Conformance to Web Content Accessibility Guidelines 1.0 -
- Copyright and legal notices -
Time to create this page: 3.3 ms