b97fdb57a2
Reviewed-by: Rich Salz <rsalz@openssl.org> (Merged from https://github.com/openssl/openssl/pull/1900)
79 lines
2.3 KiB
Text
79 lines
2.3 KiB
Text
=pod
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=head1 NAME
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RAND_add, RAND_seed, RAND_status, RAND_event, RAND_screen - add
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entropy to the PRNG
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=head1 SYNOPSIS
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#include <openssl/rand.h>
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void RAND_seed(const void *buf, int num);
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void RAND_add(const void *buf, int num, double entropy);
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int RAND_status(void);
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#if OPENSSL_API_COMPAT < 0x10100000L
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int RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
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void RAND_screen(void);
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#endif
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=head1 DESCRIPTION
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RAND_add() mixes the B<num> bytes at B<buf> into the PRNG state. Thus,
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if the data at B<buf> are unpredictable to an adversary, this
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increases the uncertainty about the state and makes the PRNG output
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less predictable. Suitable input comes from user interaction (random
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key presses, mouse movements) and certain hardware events. The
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B<entropy> argument is (the lower bound of) an estimate of how much
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randomness is contained in B<buf>, measured in bytes. Details about
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sources of randomness and how to estimate their entropy can be found
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in the literature, e.g. RFC 1750.
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RAND_add() may be called with sensitive data such as user entered
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passwords. The seed values cannot be recovered from the PRNG output.
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OpenSSL makes sure that the PRNG state is unique for each thread. On
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systems that provide C</dev/urandom>, the randomness device is used
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to seed the PRNG transparently. However, on all other systems, the
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application is responsible for seeding the PRNG by calling RAND_add(),
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L<RAND_egd(3)>
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or L<RAND_load_file(3)>.
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RAND_seed() is equivalent to RAND_add() when B<num == entropy>.
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RAND_event() and RAND_screen() are deprecated and should not be called.
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=head1 RETURN VALUES
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RAND_status() returns 1 if the PRNG has been seeded
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with enough data, 0 otherwise.
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RAND_event() calls RAND_poll() and returns RAND_status().
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RAND_screen calls RAND_poll().
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The other functions do not return values.
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=head1 HISTORY
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RAND_event() and RAND_screen() are deprecated since OpenSSL
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1.1.0. Use the functions described above instead.
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=head1 SEE ALSO
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L<RAND_bytes(3)>, L<RAND_egd(3)>,
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L<RAND_load_file(3)>, L<RAND_cleanup(3)>
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=head1 COPYRIGHT
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Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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