=head1 NAME
-RAND_add, RAND_seed, RAND_status, RAND_event, RAND_screen - add
-entropy to the PRNG
+RAND_add, RAND_poll, RAND_poll_ex, RAND_poll_cb,
+RAND_seed, RAND_status, RAND_event, RAND_screen
+- add randomness to the PRNG or get its status
=head1 SYNOPSIS
#include <openssl/rand.h>
- void RAND_seed(const void *buf, int num);
+ int RAND_status(void);
+
+ typedef void (*RAND_poll_cb)(void *arg,
+ const void *buf, int num, double randomness);
+ int RAND_poll_ex(RAND_poll_cb cb, void *arg);
+ int RAND_poll();
- void RAND_add(const void *buf, int num, double entropy);
+ void RAND_add(const void *buf, int num, double randomness);
+ void RAND_seed(const void *buf, int num);
- int RAND_status(void);
+Deprecated:
#if OPENSSL_API_COMPAT < 0x10100000L
- int RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
+ 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.
+Random numbers are a vital part of cryptography, including key generation,
+creating salts, etc., and software-based
+generators must be "seeded" with external randomness before they can be
+used as a cryptographically-secure pseudo-random number generator (CSPRNG).
+The availability of common hardware with special instructions and
+modern operating systems, which may use items such as interrupt jitter
+and network packet timings, can be reasonable sources of seeding material.
+
+RAND_status() indicates whether or not the CSPRNG has been sufficiently
+seeded. If not, functions such as RAND_bytes(3) will fail.
+
+RAND_poll_ex() uses the system's capabilities to obtain a buffer
+containing random bits which can then be used to seed a CSPRNG. The
+exact features used depends on how OpenSSL was configured, and a summary
+can be displayed with the OpenSSL L<version(1)> command. This function
+is normally called as needed by the CSPRNG. The B<arg> parameter is an
+arbitrary pointer which will be passed as an argument to the callback.
+The B<cb> function is called each time there is data to add.
+
+RAND_poll() invokes RAND_poll_ex() with B<cb> and B<arg> set so that it
+will call RAND_add(), to add the randomness to the global CSPRNG.
+
+RAND_add() mixes the B<num> bytes at B<buf> into the PRNG state.
+The B<randomness> argument is an estimate of how much randomness is
+contained in
+B<buf>, in bytes, and should be a number between zero and B<num>.
+Details about sources of randomness and how to estimate their randomness
+can be found in the literature; for example NIST SP 800-90B.
+The content of B<buf> cannot be recovered from subsequent CSPRNG output.
+This function will not normally be needed, as RAND_poll() should have been
+configured to do the appropriate seeding for the local platform.
+Applications that need to keep random state in an external file should
+use L<RAND_load_file(3)>.
+
+RAND_seed() is equivalent to RAND_add() with B<randomness> set to B<num>.
+
+RAND_event() and RAND_screen() are equivalent to RAND_poll().
=head1 RETURN VALUES
-RAND_status() returns 1 if the PRNG has been seeded
+RAND_status() returns 1 if the CSPRNG has been seeded
with enough data, 0 otherwise.
-RAND_event() calls RAND_poll() and returns RAND_status().
+RAND_poll() returns 1 if it generated seed data, 0 otherwise.
-RAND_screen calls RAND_poll().
+RAND_event() returns RAND_status().
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.
+RAND_event() and RAND_screen() were deprecated in OpenSSL 1.1.0 and should
+not be used.
=head1 SEE ALSO
-L<rand(3)>, L<RAND_egd(3)>,
-L<RAND_load_file(3)>, L<RAND_cleanup(3)>
+L<RAND_bytes(3)>, L<RAND_egd(3)>,
+L<RAND_load_file(3)>
=head1 COPYRIGHT
-Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
+Copyright 2000-2017 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
projects / openssl.git / blobdiff