Update - OpenSSL 1.1.1-pre7-dev
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@@ -24,43 +24,42 @@ Deprecated:
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=head1 DESCRIPTION
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Random numbers are a vital part of cryptography, including key generation,
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creating salts, etc., and software-based
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generators must be "seeded" with external randomness before they can be
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used as a cryptographically-secure pseudo-random number generator (CSPRNG).
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The availability of common hardware with special instructions and
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modern operating systems, which may use items such as interrupt jitter
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and network packet timings, can be reasonable sources of seeding material.
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These functions can be used to seed the random generator and to check its
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seeded state.
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In general, manual (re-)seeding of the default OpenSSL random generator
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(L<RAND_OpenSSL(3)>) is not necessary (but allowed), since it does (re-)seed
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itself automatically using trusted system entropy sources.
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This holds unless the default RAND_METHOD has been replaced or OpenSSL was
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built with automatic reseeding disabled, see L<RAND(7)> for more details.
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RAND_status() indicates whether or not the CSPRNG has been sufficiently
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seeded. If not, functions such as RAND_bytes(3) will fail.
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RAND_status() indicates whether or not the random generator has been sufficiently
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seeded. If not, functions such as L<RAND_bytes(3)> will fail.
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RAND_poll() uses the system's capabilities to seed the CSPRNG using
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RAND_poll() uses the system's capabilities to seed the random generator using
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random input obtained from polling various trusted entropy sources.
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The default choice of the entropy source can be modified at build time
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using the --with-rand-seed configure option, see also the B<NOTES> section.
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A summary of the configure options can be displayed with the OpenSSL
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L<version(1)> command.
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The default choice of the entropy source can be modified at build time,
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see L<RAND(7)> for more details.
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RAND_add() mixes the B<num> bytes at B<buf> into the PRNG state.
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RAND_add() mixes the B<num> bytes at B<buf> into the internal state
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of the random generator.
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This function will not normally be needed, as mentioned above.
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The B<randomness> argument is an estimate of how much randomness is
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contained in
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B<buf>, in bytes, and should be a number between zero and B<num>.
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Details about sources of randomness and how to estimate their randomness
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can be found in the literature; for example NIST SP 800-90B.
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The content of B<buf> cannot be recovered from subsequent CSPRNG output.
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This function will not normally be needed, as RAND_poll() should have been
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configured to do the appropriate seeding for the local platform.
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Applications that need to keep random state in an external file should
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use L<RAND_load_file(3)>.
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can be found in the literature; for example [NIST SP 800-90B].
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The content of B<buf> cannot be recovered from subsequent random generator output.
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Applications that intend to save and restore random state in an external file
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should consider using L<RAND_load_file(3)> instead.
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RAND_seed() is equivalent to RAND_add() with B<randomness> set to B<num>.
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RAND_event() and RAND_screen() are equivalent to RAND_poll().
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RAND_event() and RAND_screen() are equivalent to RAND_poll() and exist
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for compatibility reasons only. See HISTORY section below.
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=head1 RETURN VALUES
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RAND_status() returns 1 if the CSPRNG has been seeded
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RAND_status() returns 1 if the random generator has been seeded
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with enough data, 0 otherwise.
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RAND_poll() returns 1 if it generated seed data, 0 otherwise.
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@@ -69,72 +68,6 @@ RAND_event() returns RAND_status().
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The other functions do not return values.
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=head1 NOTES
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The new OpenSSL DRBG has some peculiarities which need to be taken
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into account when it is selected as the default OpenSSL CSPRNG, i.e.,
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when RAND_get_rand_method() == RAND_OpenSSL().
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This applies in particular to the way reseeding is done by the DRBG:
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=over 2
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=item *
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The DRBG seeds itself automatically, pulling random input from trusted
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entropy sources.
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Automatic reseeding occurs after a predefined number of generate requests.
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The selection of the trusted entropy sources is configured at build
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time using the --with-rand-seed option.
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=item *
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The DRBG distinguishes two different types of random input:
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'entropy', which comes from a trusted source, and 'additional input',
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which can optionally be added by the user and is considered untrusted.
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=back
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Automatic seeding can be disabled using the --with-rand-seed=none option.
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=head2 DRBG with automatic seeding enabled
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Calling RAND_poll() or RAND_add() is not necessary, because the DRBG
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polls the entropy source automatically.
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However, both calls are permitted, and do reseed the RNG.
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RAND_add() can be used to add both kinds of random input, depending on the
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value of the B<randomness> argument:
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=over 4
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=item randomness == 0:
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The random bytes are mixed as additional input into the current state of
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the DRBG.
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Mixing in additional input is not considered a full reseeding, hence the
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reseed counter is not reset.
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=item randomness > 0:
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The random bytes are used as entropy input for a full reseeding
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(resp. reinstantiation) if the DRBG is instantiated
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(resp. uninstantiated or in an error state).
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A reseeding requires 16 bytes (128 bits) of randomness.
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It is possible to provide less randomness than required.
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In this case the missing randomness will be obtained by pulling random input
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from the trusted entropy sources.
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=back
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=head2 DRBG with automatic seeding disabled (--with-rand-seed=none)
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Calling RAND_poll() will always fail.
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RAND_add() needs to be called for initial seeding and periodic reseeding.
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At least 16 bytes (128 bits) of randomness have to be provided, otherwise
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the (re-)seeding of the DRBG will fail.
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=head1 HISTORY
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RAND_event() and RAND_screen() were deprecated in OpenSSL 1.1.0 and should
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@@ -142,12 +75,14 @@ not be used.
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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)>
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L<RAND_bytes(3)>,
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L<RAND_egd(3)>,
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L<RAND_load_file(3)>,
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L<RAND(7)>
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=head1 COPYRIGHT
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Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
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Copyright 2000-2018 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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