NAME

       genrsa - generate an RSA private key

SYNOPSIS

       openssl genrsa [-out filename] [-passout arg] [-des] [-des3] [-idea] [-f4] [-3] [-rand file(s)] [-engine
       id] [numbits]

DESCRIPTION

       The genrsa command generates an RSA private key.

OPTIONS

       -out filename
           the output filename. 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).

       -des|-des3|-idea
           These options encrypt the private key with the DES, triple DES,  or  the  IDEA  ciphers  respectively
           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 a 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
           the  size of the private key to generate in bits. This must be the last option specified. The default
           is 512.

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)

1.0.1f                                             2014-01-06                                       GENRSA(1SSL)