1GENRSA(1)                           OpenSSL                          GENRSA(1)
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NAME

6       openssl-genrsa, genrsa - generate an RSA private key
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SYNOPSIS

9       openssl genrsa [-help] [-out filename] [-passout arg] [-aes128]
10       [-aes192] [-aes256] [-aria128] [-aria192] [-aria256] [-camellia128]
11       [-camellia192] [-camellia256] [-des] [-des3] [-idea] [-f4] [-3] [-rand
12       file...]  [-writerand file] [-engine id] [-primes num] [numbits]
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DESCRIPTION

15       The genrsa command generates an RSA private key.
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OPTIONS

18       -help
19           Print out a usage message.
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21       -out filename
22           Output the key to the specified file. If this argument is not
23           specified then standard output is used.
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25       -passout arg
26           The output file password source. For more information about the
27           format of arg see "Pass Phrase Options" in openssl(1).
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29       -aes128, -aes192, -aes256, -aria128, -aria192, -aria256, -camellia128,
30       -camellia192, -camellia256, -des, -des3, -idea
31           These options encrypt the private key with specified cipher before
32           outputting it. If none of these options is specified no encryption
33           is used. If encryption is used a pass phrase is prompted for if it
34           is not supplied via the -passout argument.
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36       -F4|-3
37           The public exponent to use, either 65537 or 3. The default is
38           65537.
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40       -rand file...
41           A file or files containing random data used to seed the random
42           number generator.  Multiple files can be specified separated by an
43           OS-dependent character.  The separator is ; for MS-Windows, , for
44           OpenVMS, and : for all others.
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46       [-writerand file]
47           Writes random data to the specified file upon exit.  This can be
48           used with a subsequent -rand flag.
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50       -engine id
51           Specifying an engine (by its unique id string) will cause genrsa to
52           attempt to obtain a functional reference to the specified engine,
53           thus initialising it if needed. The engine will then be set as the
54           default for all available algorithms.
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56       -primes num
57           Specify the number of primes to use while generating the RSA key.
58           The num parameter must be a positive integer that is greater than 1
59           and less than 16.  If num is greater than 2, then the generated key
60           is called a 'multi-prime' RSA key, which is defined in RFC 8017.
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62       numbits
63           The size of the private key to generate in bits. This must be the
64           last option specified. The default is 2048 and values less than 512
65           are not allowed.
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NOTES

68       RSA private key generation essentially involves the generation of two
69       or more prime numbers. When generating a private key various symbols
70       will be output to indicate the progress of the generation. A .
71       represents each number which has passed an initial sieve test, + means
72       a number has passed a single round of the Miller-Rabin primality test,
73       * means the current prime starts a regenerating progress due to some
74       failed tests. A newline means that the number has passed all the prime
75       tests (the actual number depends on the key size).
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77       Because key generation is a random process the time taken to generate a
78       key may vary somewhat. But in general, more primes lead to less
79       generation time of a key.
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SEE ALSO

82       gendsa(1)
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85       Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
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87       Licensed under the OpenSSL license (the "License").  You may not use
88       this file except in compliance with the License.  You can obtain a copy
89       in the file LICENSE in the source distribution or at
90       <https://www.openssl.org/source/license.html>.
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941.1.1k                            2021-03-26                         GENRSA(1)
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