openssl-genrsa, genrsa - generate an RSA private key
openssl genrsa [-help] [-out filename] [-passout
arg] [-aes128] [-aes192] [-aes256] [-aria128]
[-aria192] [-aria256] [-camellia128]
[-camellia192] [-camellia256] [-des] [-des3]
[-idea] [-f4] [-3] [-rand file...] [-writerand
file] [-engine id] [-primes num] [numbits]
The genrsa command generates an RSA private key.
RSA 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).
- 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 "Pass Phrase Options" 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
generator. Multiple files can be specified separated by an OS-dependent
character. The separator is ; for MS-Windows, , for OpenVMS,
and : for all others.
- [-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
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.
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Licensed under the OpenSSL license (the "License"). You
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