/usr/man/cat.1/genrsa.1

GENRSA(1)                    OpenSSL                    GENRSA(1)

NAME

     openssl-genrsa, genrsa - generate an RSA private key

SYNOPSIS

     openssl genrsa [-help] [-out filename] [-passout arg]
     [-aes128] [-aes192] [-aes256] [-aria128] [-aria192]
     [-aria256] [-camellia128] [-camellia192] [-camellia256]
     [-des] [-des3] [-idea] [-f4] [-3] [-rand file(s)] [-engine
     id] [numbits]

DESCRIPTION

     The genrsa command generates an RSA private key.

OPTIONS

     -help
         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.

     -F4|-3
         the public exponent to use, either 65537 or 3. The
         default is 65537.

     -rand file(s)
         a file or files containing random data used to seed the
         random number generator, or an EGD socket (see
         RAND_egd(3)).  Multiple files can be specified separated
         by an OS-dependent character.  The separator is ; for
         MS-Windows, , for OpenVMS, and : for all others.

     -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.

     numbits

1.0.2t               Last change: 2019-09-10                    1

GENRSA(1)                    OpenSSL                    GENRSA(1)

         the size of the private key to generate in bits. This
         must be the last option specified. The default is 2048.

NOTES

     RSA private key generation essentially involves the
     generation of two 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. 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.

BUGS

     A quirk of the prime generation algorithm is that it cannot
     generate small primes. Therefore the number of bits should
     not be less that 64. For typical private keys this will not
     matter because for security reasons they will be much larger
     (typically 1024 bits).

SEE ALSO

     gendsa(1)

COPYRIGHT

     Copyright 2000-2017 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
     <https://www.openssl.org/source/license.html>.

1.0.2t               Last change: 2019-09-10                    2

See also openssl-genrsa(1)