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Content-type: text/html
<HTML><HEAD><TITLE>Manpage of IPSEC_RSASIGKEY</TITLE>
</HEAD><BODY>
<H1>IPSEC_RSASIGKEY</H1>
Section: Maintenance Commands (8)<BR>Updated: 22 July 2001<BR><A HREF="#index">Index</A>
<A HREF="http://localhost/cgi-bin/man/man2html">Return to Main Contents</A><HR>
<A NAME="lbAB"> </A>
<H2>NAME</H2>
ipsec rsasigkey - generate RSA signature key
<A NAME="lbAC"> </A>
<H2>SYNOPSIS</H2>
<B>ipsec</B>
<B>rsasigkey</B>
[
<B>--verbose</B>
] [
<B>--random</B>
filename
]
<B>\</B>
<BR>
[
<B>--rounds</B>
nr
] [
<B>--hostname</B>
host ] [
<B>--noopt</B>
] nbits
<BR>
<B>ipsec</B>
<B>rsasigkey</B>
[
<B>--verbose</B>
] [
<B>--hostname</B>
host ]
<B>\</B>
<BR>
[
<B>--noopt</B>
]
<B>--oldkey</B>
file
<A NAME="lbAD"> </A>
<H2>DESCRIPTION</H2>
<I>Rsasigkey</I>
generates an RSA public/private key pair,
suitable for digital signatures,
of (exactly)
<I>nbits</I>
bits (that is, two primes each of exactly
<I>nbits</I>/2
bits,
and related numbers)
and emits it on standard output as ASCII (mostly hex) data.
<I>nbits</I>
must be a multiple of 16.
<P>
The public exponent is forced to the value
<B>3</B>,
which has important speed advantages for signature checking.
Beware that the resulting keys have known weaknesses as encryption keys
<I>and should not be used for that purpose</I>.
<P>
The
<B>--verbose</B>
option makes
<I>rsasigkey</I>
give a running commentary on standard error.
By default, it works in silence until it is ready to generate output.
<P>
The
<B>--random</B>
option specifies a source for random bits.
The default is
<I>/dev/random</I>
(see
<I><A HREF="random.4.html">random</A></I>(4)).
Normally,
<I>rsasigkey</I>
reads exactly
<I>nbits</I>
random bits from the source;
in extremely-rare circumstances it may need more.
<P>
The
<B>--rounds</B>
option specifies the number of rounds to be done by the
<I>mpz_probab_prime_p</I>
probabilistic primality checker.
The default, 30, is fairly rigorous and should not normally
have to be overridden.
<P>
The
<B>--hostname</B>
option specifies what host name to use in
the first line of the output (see below);
the default is what
<I><A HREF="gethostname.2.html">gethostname</A></I>(2)
returns.
<P>
The
<B>--noopt</B>
option suppresses an optimization of the private key
(to be precise, setting of the decryption exponent to
<B>lcm(p-1,q-1)</B>
rather than
<B>(p-1)*(q-1)</B>)
which speeds up operations on it slightly
but can cause it to flunk a validity check in old RSA implementations
(notably, obsolete versions of
<I><A HREF="ipsec_pluto.8.html">ipsec_pluto</A></I>(8)).
<P>
The
<B>--oldkey</B>
option specifies that rather than generate a new key,
<I>rsasigkey</I>
should read an old key from the
<I>file</I>
(the name
<B>-</B>
means ``standard input'')
and use that to generate its output.
Input lines which do not look like
<I>rsasigkey</I>
output are silently ignored.
This permits updating old keys to the current format.
<P>
The output format looks like this (with long numbers trimmed down
for clarity):
<P>
<PRE>
# RSA 2048 bits xy.example.com Sat Apr 15 13:53:22 2000
# for signatures only, UNSAFE FOR ENCRYPTION
#pubkey=0sAQOF8tZ2NZt...Y1P+buFuFn/
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
</PRE>
<P>
The first (comment) line,
indicating the nature and date of the key,
and giving a host name,
is used by
<I><A HREF="ipsec_showhostkey.8.html">ipsec_showhostkey</A></I>(8)
when generating some forms of key output.
<P>
The commented-out
<B>pubkey=</B>
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
<B>0s</B>
prefix, rather than in unadorned base-64),
suitable for use in the
<I>ipsec.conf</I>
file.
<P>
The
<B>Modulus</B>,
<B>PublicExponent</B>,
and
<B>PrivateExponent</B>
lines give the basic signing and verification data.
<P>
The
<B>Prime1</B>
and
<B>Prime2</B>
lines give the primes themselves (aka
<I>p</I>
and
<I>q</I>),
largest first.
The
<B>Exponent1</B>
and
<B>Exponent2</B>
lines give
the private exponent mod
<I>p-1</I>
and
<I>q-1</I>
respectively.
The
<B>Coefficient</B>
line gives the Chinese Remainder Theorem coefficient,
which is the inverse of
<I>q</I>,
mod
<I>p</I>.
These additional numbers (which must all be kept as secret as the
private exponent) are precomputed aids to rapid signature generation.
<P>
No attempt is made to break long lines.
<P>
The US patent on the RSA algorithm expired 20 Sept 2000.
<A NAME="lbAE"> </A>
<H2>EXAMPLES</H2>
<DL COMPACT>
<DT><B>ipsec rsasigkey --verbose 2192 >mykey</B>
<DD>
generates a 2192-bit signature key and puts it in the file
<I>mykey</I>,
with running commentary on standard error.
The file contents can be inserted verbatim into a suitable entry in the
<I>ipsec.secrets</I>
file (see
<I><A HREF="ipsec.secrets.5.html">ipsec.secrets</A></I>(5)),
and the public key can then be extracted and edited into the
<I>ipsec.conf</I>
file (see
<I><A HREF="ipsec.conf.5.html">ipsec.conf</A></I>(5)).
<DT><B>ipsec rsasigkey --verbose --oldkey oldie >latest</B>
<DD>
takes the old signature key from file
<I>oldie</I>
and puts a version in the current format into the file
<I>latest</I>,
with running commentary on standard error.
</DL>
<A NAME="lbAF"> </A>
<H2>FILES</H2>
/dev/random
<A NAME="lbAG"> </A>
<H2>SEE ALSO</H2>
<A HREF="random.4.html">random</A>(4), <A HREF="ipsec_showhostkey.8.html">ipsec_showhostkey</A>(8)
<BR>
<I>Applied Cryptography</I>, 2nd. ed., by Bruce Schneier, Wiley 1996.
<BR>
RFCs 2537, 2313.
<BR>
<I>GNU MP, the GNU multiple precision arithmetic library, edition 2.0.2</I>,
by Torbj Granlund.
<A NAME="lbAH"> </A>
<H2>HISTORY</H2>
Written for the Linux FreeS/WAN project
<<A HREF="http://www.freeswan.org">http://www.freeswan.org</A>>
by Henry Spencer.
<A NAME="lbAI"> </A>
<H2>BUGS</H2>
There is an internal limit on
<I>nbits</I>,
currently 20000.
<P>
<I>Rsasigkey</I>'s
run time is difficult to predict,
since
<I>/dev/random</I>
output can 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 200MHz 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.
<P>
The
<B>--oldkey</B>
option does not check its input format as rigorously as it might.
Corrupted
<I>rsasigkey</I>
output may confuse it.
<P>
<HR>
<A NAME="index"> </A><H2>Index</H2>
<DL>
<DT><A HREF="#lbAB">NAME</A><DD>
<DT><A HREF="#lbAC">SYNOPSIS</A><DD>
<DT><A HREF="#lbAD">DESCRIPTION</A><DD>
<DT><A HREF="#lbAE">EXAMPLES</A><DD>
<DT><A HREF="#lbAF">FILES</A><DD>
<DT><A HREF="#lbAG">SEE ALSO</A><DD>
<DT><A HREF="#lbAH">HISTORY</A><DD>
<DT><A HREF="#lbAI">BUGS</A><DD>
</DL>
<HR>
This document was created by
<A HREF="http://localhost/cgi-bin/man/man2html">man2html</A>,
using the manual pages.<BR>
Time: 21:40:18 GMT, November 11, 2003
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