genrsa - generate an RSA private key


SYNOPSIS

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

       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).

       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)


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