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       ipsec_rsasigkey - generate RSA signature key


       ipsec rsasigkey [--verbose] [--random filename] [--rounds nr]
             [--configdir nssdbdir] [--password nsspassword]
             [--hostname hostname] [--noopt] nbits

       ipsec rsasigkey [--verbose] [--configdir nssdbdir]
             [--password nsspassword] [--hostname hostname] [--noopt]
             [--oldkey filename]


       Rsasigkey generates an RSA public/private key pair, suitable for
       digital signatures, of (exactly) nbits bits (that is, two primes each
       of exactly nbits/2 bits, and related numbers) and emits it on standard
       output as ASCII (mostly hex) data.  nbits must be a multiple of 16.

       The public exponent is forced to the value 3, which has important speed
       advantages for signature checking. Beware that the resulting keys have
       known weaknesses as encryption keys and should not be used for that

       The --verbose option makesrsasigkey give a running commentary on
       standard error. By default, it works in silence until it is ready to
       generate output.

       The --random option specifies a source for random bits. The default is
       /dev/random (see random(4)). Normally, rsasigkey reads exactly nbits
       random bits from the source; in extremely-rare circumstances it may
       need more. Under Linux with hardware random support, the special device
       /dev/hw_random is created. However, the driver does not guarantee FIPS
       compliant random, and some hardware is so broken that it return
       extremely non-random data. Therefor /dev/hw_random should never be used
       with the --random option. Instead, one should run the rngd(8) daemon to
       funnel randomness from /dev/hw_random into /dev/random.

       The --rounds option specifies the number of rounds to be done by the
       pz_probab_prime_p probabilistic primality checker. The default, 30, is
       fairly rigorous and should not normally have to be overridden.

       The --Configdir option specifies the nss configuration directory to
       use. This is the directory where the NSS certificate, key and security
       modules databases reside.

       The --password option specifies the nss cryptographic module
       authentication password if the NSS module has been configured to
       require it. A password is required by hardware tokens and also by the
       internal softotken module when configured to run in FIPS mode.

       The --hostname option specifies what host name to use in the first line
       of the output (see below); the default is what gethostname(2) returns.

       The --hostname option suppresses an optimization of the private key (to
       be precise, setting of the decryption exponent to lcm(p-1,q-1) rather
       than (p-1)*(q-1)) which speeds up operations on it slightly but can
       cause it to flunk a validity check in old RSA implementations (notably,
       obsolete versions of ipsec_pluto(8)

       --oldkey option specifies that rather than generate a new key,
       rsasigkey should read an old key from the file (the name ’-’ means
       "standard input") and use that to generate its output. Input lines
       which do not look like rsasigkey output are silently ignored. This
       permits updating old keys to the current format.

       The output format looks like this (with long numbers trimmed down for

                # RSA 2048 bits   Sat Apr 15 13:53:22 2000
                # for signatures only, UNSAFE FOR ENCRYPTION
                Modulus: 0xcc2a86fcf440...cf1011abb82d1
                PublicExponent: 0x03
                # everything after this point is secret
                PrivateExponent: 0x881c59fdf8...ab05c8c77d23
                Prime1: 0xf49fd1f779...46504c7bf3
                Prime2: 0xd5a9108453...321d43cb2b
                Exponent1: 0xa31536a4fb...536d98adda7f7
                Exponent2: 0x8e70b5ad8d...9142168d7dcc7
                Coefficient: 0xafb761d001...0c13e98d98

       The first (comment) line, indicating the nature and date of the key,
       and giving a host name, is used by ipsec_showhostkey(8) when generating
       some forms of key output.

       The commented-out pubkey= line contains the public key, the public
       exponent and the modulus combined in approximately RFC 2537 format (the
       one deviation is that the combined value is given with a 0s prefix,
       rather than in unadorned base-64), suitable for use in the ipsec.conf

       The Modulus, PublicExponent and PrivateExponent lines give the basic
       signing and verification data.

       The Prime1 and Prime2 lines give the primes themselves (aka p and q),
       largest first. The Exponent1 and Exponent2 lines give the private
       exponent mod p-1 and q-1 respectively. The Coefficient line gives the
       Chinese Remainder Theorem coefficient, which is the inverse of q, mod
       p. These additional numbers (which must all be kept as secret as the
       private exponent) are precomputed aids to rapid signature generation.

       No attempt is made to break long lines.

       The US patent on the RSA algorithm expired 20 Sept 2000.


       ipsec rsasigkey --verbose 2192 >mykey.txt
           generates a 2192-bit signature key and puts it in the file
           mykey.txt, with running commentary on standard error. The file
           contents can be inserted verbatim into a suitable entry in the
           ipsec.secrets file (see ipsec_secrets(5)), and the public key can
           then be extracted and edited into the ipsec.conf (see

       ipsec rsasigkey --verbose --oldkey oldie >latest.txt
           takes the old signature key from file oldie and puts a version in
           the current format into the file latest, with running commentary on
           standard error.


       /dev/random, /dev/urandom


       random(4), rngd(8), ipsec_showhostkey(8), Applied Cryptography, 2nd.
       ed., by Bruce Schneier, Wiley 1996, RFCs 2537, 2313, GNU MP, the GNU
       multiple precision arithmetic library, edition 2.0.2, by Torbj Granlund


       Written for the Linux FreeS/WAN project <> by
       Henry Spencer.


       There is an internal limit on nbits, currently 20000.

       rsasigkey’s run time is difficult to predict, since /dev/random
       outputcan be arbitrarily delayed if the system’s entropy pool is low on
       randomness, and the time taken by the search for primes is also
       somewhat unpredictable. A reasonably typical time for a 1024-bit key on
       a quiet 00MHz Pentium MMX with plenty of randomness available is 20
       seconds, almost all of it in the prime searches. Generating a 2192-bit
       key on the same system usually takes several minutes. A 4096-bit key
       took an hour and a half of CPU time.

       The --oldkey option does not check its input format as rigorously as it
       might. Corrupted rsasigkey output may confuse it.

[FIXME: source]                   03/09/2010