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 stan-
   dard 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 num-
   ber generator, or an EGD socket (see RAND_egd(3)). Multiple files
   can be specified separated by a OS-dependent character. The sepa-
   rator is ; for MS-Windows, , for OpenVMS, and : for all others.

    -engine id
   specifying an engine (by it's unique id string) will cause req 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)