Section: OpenSSL (1)
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openssl-genrsa, genrsa - generate an RSA private key
command generates an RSA
Print out a usage message.
- -out filename
Output the key to the specified file. If this argument is not specified then
standard output is used.
- -passout arg
The output file password source. For more information about the format
of arg see the PASS PHRASE ARGUMENTS section in openssl(1).
- -aes128, -aes192, -aes256, -aria128, -aria192, -aria256, -camellia128, -camellia192, -camellia256, -des, -des3, -idea
These options encrypt the private key with specified
cipher before outputting it. If none of these options is
specified no encryption is used. If encryption is used a pass phrase is prompted
for if it is not supplied via the -passout argument.
The public exponent to use, either 65537 or 3. The default is 65537.
- -rand file...
A file or files containing random data used to seed the random number
Multiple files can be specified separated by an OS-dependent character.
The separator is ; for MS-Windows, , for OpenVMS, and : for
- [-writerand file]
Writes random data to the specified file upon exit.
This can be used with a subsequent -rand flag.
- -engine id
Specifying an engine (by its unique id string) will cause genrsa
to attempt to obtain a functional reference to the specified engine,
thus initialising it if needed. The engine will then be set as the default
for all available algorithms.
- -primes num
Specify the number of primes to use while generating the RSA key. The num
parameter must be a positive integer that is greater than 1 and less than 16.
If num is greater than 2, then the generated key is called a 'multi-prime'
RSA key, which is defined in RFC 8017.
The size of the private key to generate in bits. This must be the last option
specified. The default is 2048 and values less than 512 are not allowed.
private key generation essentially involves the generation of two or more
prime numbers. When generating a private key various symbols will be output to
indicate the progress of the generation. A .
represents each number which
has passed an initial sieve test, +
means a number has passed a single
round of the Miller-Rabin primality test, *
means the current prime starts
a regenerating progress due to some failed tests. A newline means that the number
has passed all the prime tests (the actual number depends on the key size).
Because key generation is a random process the time taken to generate a key
may vary somewhat. But in general, more primes lead to less generation time
of a key.
Copyright 2000-2018 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
in the file LICENSE in the source distribution or at