96 lines
2.4 KiB
Plaintext
96 lines
2.4 KiB
Plaintext
=pod
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=head1 NAME
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openssl-rand,
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rand - generate pseudo-random bytes
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=head1 SYNOPSIS
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B<openssl rand>
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[B<-help>]
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[B<-out> I<file>]
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[B<-rand file...>]
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[B<-writerand file>]
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[B<-base64>]
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[B<-hex>]
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I<num>
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=head1 DESCRIPTION
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This command generates I<num> random bytes using a cryptographically
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secure pseudo random number generator (CSPRNG).
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The random bytes are generated using the L<RAND_bytes(3)> function,
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which provides a security level of 256 bits, provided it managed to
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seed itself successfully from a trusted operating system entropy source.
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Otherwise, the command will fail with a nonzero error code.
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For more details, see L<RAND_bytes(3)>, L<RAND(7)>, and L<RAND_DRBG(7)>.
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=head1 OPTIONS
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=over 4
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=item B<-help>
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Print out a usage message.
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=item B<-out file>
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Write to I<file> instead of standard output.
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=item B<-rand file...>
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A file or files containing random data used to seed the random number
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generator.
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Multiple files can be specified separated by an OS-dependent character.
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The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
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all others.
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Explicitly specifying a seed file is in general not necessary, see the
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L</NOTES> section for more information.
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=item [B<-writerand file>]
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Writes random data to the specified I<file> upon exit.
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This can be used with a subsequent B<-rand> flag.
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=item B<-base64>
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Perform base64 encoding on the output.
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=item B<-hex>
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Show the output as a hex string.
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=back
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=head1 NOTES
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Prior to OpenSSL 1.1.1, it was common for applications to store information
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about the state of the random-number generator in a file that was loaded
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at startup and rewritten upon exit. On modern operating systems, this is
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generally no longer necessary as OpenSSL will seed itself from a trusted
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entropy source provided by the operating system. The B<-rand> and
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B<-writerand> flags are still supported for special platforms or
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circumstances that might require them.
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It is generally an error to use the same seed file more than once and
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every use of B<-rand> should be paired with B<-writerand>.
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=head1 SEE ALSO
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L<RAND_bytes(3)>,
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L<RAND(7)>,
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L<RAND_DRBG(7)>
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=head1 COPYRIGHT
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Copyright 2000-2020 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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