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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