NAME

       genrsa - generate an RSA private key

SYNOPSIS

       openssl genrsa [-out filename] [-passout arg] [-aes128] [-aes192] [-aes256] [-camellia128] [-camellia192]
       [-camellia256] [-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).

       -aes128|-aes192|-aes256|-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  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)

1.0.2g                                             2016-03-01                                       GENRSA(1SSL)