Openssl 1.1.0h

doc/crypto/RAND_add.pod

@@ -0,0 +1,79 @@
+=pod
+
+=head1 NAME
+
+RAND_add, RAND_seed, RAND_status, RAND_event, RAND_screen - add
+entropy to the PRNG
+
+=head1 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);
+
+ #if OPENSSL_API_COMPAT < 0x10100000L
+ int  RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
+ void RAND_screen(void);
+ #endif
+
+=head1 DESCRIPTION
+
+RAND_add() mixes the B<num> bytes at B<buf> into the PRNG state. Thus,
+if the data at B<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
+B<entropy> argument is (the lower bound of) an estimate of how much
+randomness is contained in B<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 C</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(),
+L<RAND_egd(3)>
+or L<RAND_load_file(3)>.
+
+RAND_seed() is equivalent to RAND_add() when B<num == entropy>.
+
+RAND_event() and RAND_screen() are deprecated and should not be called.
+
+=head1 RETURN VALUES
+
+RAND_status() returns 1 if the PRNG has been seeded
+with enough data, 0 otherwise.
+
+RAND_event() calls RAND_poll() and returns RAND_status().
+
+RAND_screen calls RAND_poll().
+
+The other functions do not return values.
+
+=head1 HISTORY
+
+RAND_event() and RAND_screen() are deprecated since OpenSSL
+1.1.0.  Use the functions described above instead.
+
+=head1 SEE ALSO
+
+L<rand(3)>, L<RAND_egd(3)>,
+L<RAND_load_file(3)>, L<RAND_cleanup(3)>
+
+=head1 COPYRIGHT
+
+Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the OpenSSL license (the "License").  You may not use
+this file except in compliance with the License.  You can obtain a copy
+in the file LICENSE in the source distribution or at
+L<https://www.openssl.org/source/license.html>.
+
+=cut