README

Copyright (C)  2002, 2003, 2004, 2005, 2006, 2007, 2009,
               2015, 2016, 2017, 2018, 2019  Heiko Stamer <HeikoStamer@gmx.net>

Permission is granted to copy, distribute and/or modify this document under
the terms of the GNU Free Documentation License, Version 1.3 or any later
version published by the Free Software Foundation; with no Invariant Sections,
no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included
in the sources of this package and additionally can be obtained from Internet
<https://www.gnu.org/licenses>.

Introduction
------------

  SecureSkat is a peer-to-peer implementation of the card game Skat.
  
  The program negotiates possible players and sessions over an arbitrary
  IRC network (Internet Relay Chat). It uses the C++ library LibTMCG to
  ensure a reasonable level of verifiablility for card operations.
  Furthermore, SecureSkat provides electronic voting capabilities based
  on a simple playing card encoding.

  LibTMCG provides interfaces for creating secure and verifiable online card
  games without depending on a trusted third-party (TTP). The corresponding
  cryptographic problem, actually called "Mental Poker", has been studied
  since 1979 (Shamir, Rivest, and Adleman) by many authors.
                      (see https://www.nongnu.org/libtmcg for more details)


Requirements
------------

  You need the following libraries and appropriate header files to build
  (GCC version >= 5.x.y is recommended) `SecureSkat' successfully:

  * Toolbox for Mental Card Games (LibTMCG), version >= 1.3.18
    https://www.nongnu.org/libtmcg/

  * GNU Multiple Precision Arithmetic Library (libgmp), version >= 4.2
    https://gmplib.org/

  * GNU Crypto Library (libgcrypt), version >= 1.6.0
    https://www.gnupg.org/software/libgcrypt/index.html

  * GNU Readline Library (libreadline), version >= 4.3
    https://www.gnu.org/

  * GNU Database Manager (libgdbm), version >= 1.8.0
    https://www.gnu.org/

  * ncurses Library (libncurses), version >= 5.0
    
  * zlib Compression Library (libz)

  SecureSkat was tested (+ successful, - with errors) on following platforms:

  + GNU/Linux (Gentoo Linux)    x86_64      gcc 9.1.0
  + GNU/Linux (Debian)          x86_64      gcc 6.3.0
  + GNU/Linux (Ubuntu 16.04.2)	x86_64      gcc 5.4.0
  + GNU/Linux (Trisquel Linux)  x86_64      gcc 4.8.4
  + OpenBSD 6.4                 amd64       gcc 4.2.1
  + FreeBSD 12.0                amd64       gcc 8.2.0

Build & Install
---------------

  1. ./configure

  2. make

  3. make install

Playing SecureSkat over an IRC network
--------------------------------------

  Please run 'SecureSkat <IRC_SERVER> [<IRC_PORT> [<CTRL_PROGRAM>]]',
  where
    <IRC_SERVER> is the hostname of a RFC1459 conform IRC server,
    <IRC_PORT> is the TCP port number of this server, e.g. 6667, and
    <CTRL_PROGRAM> is an interface control program, e.g. SecureSkat_random.
    (Note: Please give always the full path to the binary file here!)

  The last two arguments are optional. In that case, IRC port number
  is set to 6667 and no interface control program will be used.
  Currently, only one control program is included in this distribution:
  
    SecureSkat_random : the random computer player (a very weak opponent)
  
  At first time (i.e. the file '~/.SecureSkat/SecureSkat.skr' does not
  exist yet) the program will ask you for a nickname and an email address.
  You have to provide two non-empty strings, hopefully honest information.
  Afterwards your secret key is created and stored in the GDBM database
  '~/.SecureSkat/SecureSkat.skr'. You can choose a pass phrase to protect
  the key by encryption (Blowfish-128, CFB mode). This feature is turned
  off (for the reason of backward compatibility), if an empty phrase is
  provided. Additionally it may be a good idea to set appropriate file
  permissions on the database.
  
  Dependent on your processor speed the key generation takes a lot of time
  until the success message `PKI: cryptographic key ID5^????? created and
  stored' is printed. ('?' is here a wildcard for some random looking
  letters and digits as a hopefully unique identity of the generated key)
  
  Later you will be registered at the IRC server with a strange nickname
  like `ID5^z34g0' (based on the key id from your public key). For large
  groups of participants collisions become probable --- in such a rare case,
  please generate a fresh key by deleting the database 'SecureSkat.skr'
  and restart again.
  
  Now you will be joined automatically to channel #openSkat (The former program
  name was kept to provide backward compatibility with older versions.) and you
  can chat with other players simply by typing lines of text. Commands are
  strings, wherein the first letter is a '/' (slash). For example, '/help'
  prints a short help screen (example follows):

    /quit               quits SecureSkat
    /on                 turns the output of IRC channel #openSkat on
    /off                turns the output of IRC channel #openSkat off
    /players            shows the list of possible participants
    /tables             shows the list of existing game tables
    /rooms              shows the list of existing ballot rooms
    /rank               computes your current rank (Extended Seeger System)
    /export <fn>        exports your public key to the file <fn>
    /import <fn>        imports a valid public key from the file <fn>
    /skat <nr> <r>      creates a new table <nr> to play <r> rounds
    /skat <nr>          joins the existing game on table <nr>
    /<nr> <cmd>         executes the following command <cmd> on table <nr>
      /<nr> view               shows your cards and additional information
      /<nr> bid                bids or justifies a bid
      /<nr> pass               passes the current biding
      /<nr> hand               leave the Skat untouched
      /<nr> skat               takes the Skat and shows the two cards
      /<nr> push <k1> <k2>     pushes the card <k1> and <k2> away
      /<nr> announce <s> [op]  announces the game <s> ([op] is optional)
      /<nr> play <k1>          plays the card <k1>
    
    <fn> is a regular file name according to the used file system
    <nr> is an arbitrary string (practically it should be a number, e.g. 001)
    <r>  is an unsigned integer (number of rounds to play, 1 round = 3 games)
    <k1>, <k2> are from { Sc, Ro, Gr, Ei } || { 7, 8, 9, U, O, K, 10, A }
    (|| denotes the concatenation of strings, e.g. Ro9 = red nine)
    <s> is from { Sc, Ro, Gr, Nu, Ei, Gd }  (Nu = Null, Gd = Grand)
    [op] is from { Sn, Sw, Ov } (Schneider, Schwarz or Ouvert announced)

  SecureSkat tries to exchange and to verify the public keys automagically.
  Therefore it binds three TCP ports (free ports up from 7771): on the first
  it exports the public key, on the second it exports a table of stored ranking
  data, and on the third it answers ranking data requests. Checking whether
  the public key is valid is done by a non-interactive zero knowledge proof
  (soundness error probability is currently fixed at 2^{-80}). Hence the
  execution of verification tasks can take some amount of time and continues
  in background until a success message `PKI identified ID?^????? aka ???...'
  ('?' is here again a wildcard) appears. Sometimes the background process is
  aborted with an appropriate error message. Well, if anything went wrong you
  may have to exchange the keys manually. Then please use the commands
  '/export <file name>' resp. '/import <file name>' to help yourself and file
  a bug report in such a rare case.

  After a successful key exchange you can start playing Skat by joining
  existing tables ('/skat <table identifier>') or by creating new tables
  ('/skat <table identifier> <number of rounds to play>'). Of course, in
  both cases you have to wait for other participants. The command '/tables'
  prints a short list of all existing tables and '/players' a list of the
  registered players, respectively. During the actual session initialization
  of the game (i.e. for each table) a TCP/IP connection with each of your
  opponents will be established. Therefore (and further for the automatic key
  exchange and ranking data gossip) your workstation's firewall or router
  must permit incoming TCP connections in the port range 7771 to 7930.

  However, there is another way to get things work: use Tor! In order to set
  an alternative hostname the environment variable ALTHOST can be used, i.e.,
  the onion address of a local hidden service with local port forwarding rules
  will do the job. Therefore you have to put the following lines (redirecting
  request to the running instance of SecureSkat) in your local torrc file:

    HiddenServiceDir /var/lib/tor/secureskat/
    HiddenServicePort 7771 127.0.0.1:7771
    HiddenServicePort 7772 127.0.0.1:7772
    HiddenServicePort 7773 127.0.0.1:7773
    HiddenServicePort 7774 127.0.0.1:7774
    HiddenServicePort 7775 127.0.0.1:7775
    HiddenServicePort 7776 127.0.0.1:7776
    HiddenServicePort 7777 127.0.0.1:7777
    HiddenServicePort 7778 127.0.0.1:7778
    HiddenServicePort 7779 127.0.0.1:7779
    HiddenServicePort 7780 127.0.0.1:7780
    HiddenServicePort 7781 127.0.0.1:7781
    HiddenServicePort 7782 127.0.0.1:7782
    HiddenServicePort 7783 127.0.0.1:7783
    HiddenServicePort 7784 127.0.0.1:7784
    HiddenServicePort 7785 127.0.0.1:7785
    HiddenServicePort 7786 127.0.0.1:7786
    HiddenServicePort 7787 127.0.0.1:7787
    HiddenServicePort 7788 127.0.0.1:7788
    HiddenServicePort 7789 127.0.0.1:7789
    HiddenServicePort 7790 127.0.0.1:7790
    HiddenServicePort 7791 127.0.0.1:7791
    HiddenServicePort 7792 127.0.0.1:7792
    HiddenServicePort 7793 127.0.0.1:7793
    HiddenServicePort 7794 127.0.0.1:7794
    HiddenServicePort 7795 127.0.0.1:7795
    HiddenServicePort 7796 127.0.0.1:7796
    HiddenServicePort 7797 127.0.0.1:7797
    HiddenServicePort 7798 127.0.0.1:7798
    HiddenServicePort 7799 127.0.0.1:7799
    HiddenServicePort 7800 127.0.0.1:7800
    HiddenServicePort 7801 127.0.0.1:7801
    HiddenServicePort 7802 127.0.0.1:7802
    HiddenServicePort 7803 127.0.0.1:7803
    HiddenServicePort 7804 127.0.0.1:7804
    HiddenServicePort 7805 127.0.0.1:7805
    HiddenServicePort 7806 127.0.0.1:7806
    HiddenServicePort 7807 127.0.0.1:7807
    HiddenServicePort 7808 127.0.0.1:7808
    HiddenServicePort 7809 127.0.0.1:7809
    HiddenServicePort 7810 127.0.0.1:7810
    HiddenServicePort 7811 127.0.0.1:7811
    HiddenServicePort 7812 127.0.0.1:7812
    HiddenServicePort 7813 127.0.0.1:7813
    HiddenServicePort 7814 127.0.0.1:7814
    HiddenServicePort 7815 127.0.0.1:7815
    HiddenServicePort 7816 127.0.0.1:7816
    HiddenServicePort 7817 127.0.0.1:7817
    HiddenServicePort 7818 127.0.0.1:7818
    HiddenServicePort 7819 127.0.0.1:7819
    HiddenServicePort 7820 127.0.0.1:7820
    HiddenServicePort 7821 127.0.0.1:7821
    HiddenServicePort 7822 127.0.0.1:7822
    HiddenServicePort 7823 127.0.0.1:7823
    HiddenServicePort 7824 127.0.0.1:7824
    HiddenServicePort 7825 127.0.0.1:7825
    HiddenServicePort 7826 127.0.0.1:7826
    HiddenServicePort 7827 127.0.0.1:7827
    HiddenServicePort 7828 127.0.0.1:7828
    HiddenServicePort 7829 127.0.0.1:7829
    HiddenServicePort 7830 127.0.0.1:7830
    HiddenServicePort 7831 127.0.0.1:7831
    HiddenServicePort 7832 127.0.0.1:7832
    HiddenServicePort 7833 127.0.0.1:7833
    HiddenServicePort 7834 127.0.0.1:7834
    HiddenServicePort 7835 127.0.0.1:7835
    HiddenServicePort 7836 127.0.0.1:7836
    HiddenServicePort 7837 127.0.0.1:7837
    HiddenServicePort 7838 127.0.0.1:7838
    HiddenServicePort 7839 127.0.0.1:7839
    HiddenServicePort 7840 127.0.0.1:7840
    HiddenServicePort 7841 127.0.0.1:7841
    HiddenServicePort 7842 127.0.0.1:7842
    HiddenServicePort 7843 127.0.0.1:7843
    HiddenServicePort 7844 127.0.0.1:7844
    HiddenServicePort 7845 127.0.0.1:7845
    HiddenServicePort 7846 127.0.0.1:7846
    HiddenServicePort 7847 127.0.0.1:7847
    HiddenServicePort 7848 127.0.0.1:7848
    HiddenServicePort 7849 127.0.0.1:7849
    HiddenServicePort 7850 127.0.0.1:7850
    HiddenServicePort 7851 127.0.0.1:7851
    HiddenServicePort 7852 127.0.0.1:7852
    HiddenServicePort 7853 127.0.0.1:7853
    HiddenServicePort 7854 127.0.0.1:7854
    HiddenServicePort 7855 127.0.0.1:7855
    HiddenServicePort 7856 127.0.0.1:7856
    HiddenServicePort 7857 127.0.0.1:7857
    HiddenServicePort 7858 127.0.0.1:7858
    HiddenServicePort 7859 127.0.0.1:7859
    HiddenServicePort 7860 127.0.0.1:7860
    HiddenServicePort 7861 127.0.0.1:7861
    HiddenServicePort 7862 127.0.0.1:7862
    HiddenServicePort 7863 127.0.0.1:7863
    HiddenServicePort 7864 127.0.0.1:7864
    HiddenServicePort 7865 127.0.0.1:7865
    HiddenServicePort 7866 127.0.0.1:7866
    HiddenServicePort 7867 127.0.0.1:7867
    HiddenServicePort 7868 127.0.0.1:7868
    HiddenServicePort 7869 127.0.0.1:7869
    HiddenServicePort 7870 127.0.0.1:7870
    HiddenServicePort 7871 127.0.0.1:7871
    HiddenServicePort 7872 127.0.0.1:7872
    HiddenServicePort 7873 127.0.0.1:7873
    HiddenServicePort 7874 127.0.0.1:7874
    HiddenServicePort 7875 127.0.0.1:7875
    HiddenServicePort 7876 127.0.0.1:7876
    HiddenServicePort 7877 127.0.0.1:7877
    HiddenServicePort 7878 127.0.0.1:7878
    HiddenServicePort 7879 127.0.0.1:7879
    HiddenServicePort 7880 127.0.0.1:7880
    HiddenServicePort 7881 127.0.0.1:7881
    HiddenServicePort 7882 127.0.0.1:7882
    HiddenServicePort 7883 127.0.0.1:7883
    HiddenServicePort 7884 127.0.0.1:7884
    HiddenServicePort 7885 127.0.0.1:7885
    HiddenServicePort 7886 127.0.0.1:7886
    HiddenServicePort 7887 127.0.0.1:7887
    HiddenServicePort 7888 127.0.0.1:7888
    HiddenServicePort 7889 127.0.0.1:7889
    HiddenServicePort 7890 127.0.0.1:7890
    HiddenServicePort 7891 127.0.0.1:7891
    HiddenServicePort 7892 127.0.0.1:7892
    HiddenServicePort 7893 127.0.0.1:7893
    HiddenServicePort 7894 127.0.0.1:7894
    HiddenServicePort 7895 127.0.0.1:7895
    HiddenServicePort 7896 127.0.0.1:7896
    HiddenServicePort 7897 127.0.0.1:7897
    HiddenServicePort 7898 127.0.0.1:7898
    HiddenServicePort 7899 127.0.0.1:7899
    HiddenServicePort 7900 127.0.0.1:7900
    HiddenServicePort 7901 127.0.0.1:7901
    HiddenServicePort 7902 127.0.0.1:7902
    HiddenServicePort 7903 127.0.0.1:7903
    HiddenServicePort 7904 127.0.0.1:7904
    HiddenServicePort 7905 127.0.0.1:7905
    HiddenServicePort 7906 127.0.0.1:7906
    HiddenServicePort 7907 127.0.0.1:7907
    HiddenServicePort 7908 127.0.0.1:7908
    HiddenServicePort 7909 127.0.0.1:7909
    HiddenServicePort 7910 127.0.0.1:7910
    HiddenServicePort 7911 127.0.0.1:7911
    HiddenServicePort 7912 127.0.0.1:7912
    HiddenServicePort 7913 127.0.0.1:7913
    HiddenServicePort 7914 127.0.0.1:7914
    HiddenServicePort 7915 127.0.0.1:7915
    HiddenServicePort 7916 127.0.0.1:7916
    HiddenServicePort 7917 127.0.0.1:7917
    HiddenServicePort 7918 127.0.0.1:7918
    HiddenServicePort 7919 127.0.0.1:7919
    HiddenServicePort 7920 127.0.0.1:7920
    HiddenServicePort 7921 127.0.0.1:7921
    HiddenServicePort 7922 127.0.0.1:7922
    HiddenServicePort 7923 127.0.0.1:7923
    HiddenServicePort 7924 127.0.0.1:7924
    HiddenServicePort 7925 127.0.0.1:7925
    HiddenServicePort 7926 127.0.0.1:7926
    HiddenServicePort 7927 127.0.0.1:7927
    HiddenServicePort 7928 127.0.0.1:7928
    HiddenServicePort 7929 127.0.0.1:7929
    HiddenServicePort 7930 127.0.0.1:7930

  You must have the following line in your torsocks.conf file activated:

    AllowInbound 1

  Last but not least, an IRC server with onion address is required. The
  appropriate command line looks like as in the following example.

    $ torsocks SecureSkat i53u25l4zprfim66.onion


Bugs, Contribution, GIT
-----------------------

  If you want to contribute, please send your detailed bug reports either
  to Heiko Stamer <HeikoStamer@gmx.net> or use the bug tracker from project
  web space at GNU/Savannah.

  You can get the latest sources from our GIT repository at GNU/Savannah.


Copyright and License of this software
--------------------------------------

  (C) 2002, 2003, 2004, 2005, 2006, 2007, 2009, 
      2015, 2016, 2017, 2018, 2019  Heiko Stamer <HeikoStamer@gmx.net>
      GNU General Public License version 2

  Please have a look at the file 'COPYING' and http://www.fsf.org/.

References
----------

[1] Heiko Stamer. Kryptographische Skatrunde. (in German)
    Offene Systeme, Number 4, pp. 10--30, 2004, ISSN 1619-0114.

[2] Heiko Stamer. Efficient Electronic Gambling: An Extended Implementation
    of the Toolbox for Mental Card Games.
    Proceedings of the Western European Workshop on Research in
    Cryptology (WEWoRC 2005), LNI P-75, pp. 1--12, 2005.

Appendix
========

GNU Free Documentation License
------------------------------


                GNU Free Documentation License
                 Version 1.3, 3 November 2008


 Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
     <http://fsf.org/>
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

0. PREAMBLE

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for modifications made by others.

This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.  It
complements the GNU General Public License, which is a copyleft
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We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
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   (which should, if there were any, be listed in the History section
   of the Document).  You may use the same title as a previous version
   if the original publisher of that version gives permission.
B. List on the Title Page, as authors, one or more persons or entities
   responsible for authorship of the modifications in the Modified
   Version, together with at least five of the principal authors of the
   Document (all of its principal authors, if it has fewer than five),
   unless they release you from this requirement.
C. State on the Title page the name of the publisher of the
   Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
   adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license notice
   giving the public permission to use the Modified Version under the
   terms of this License, in the form shown in the Addendum below.
G. Preserve in that license notice the full lists of Invariant Sections
   and required Cover Texts given in the Document's license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History", Preserve its Title, and add
   to it an item stating at least the title, year, new authors, and
   publisher of the Modified Version as given on the Title Page.  If
   there is no section Entitled "History" in the Document, create one
   stating the title, year, authors, and publisher of the Document as
   given on its Title Page, then add an item describing the Modified
   Version as stated in the previous sentence.
J. Preserve the network location, if any, given in the Document for
   public access to a Transparent copy of the Document, and likewise
   the network locations given in the Document for previous versions
   it was based on.  These may be placed in the "History" section.
   You may omit a network location for a work that was published at
   least four years before the Document itself, or if the original
   publisher of the version it refers to gives permission.
K. For any section Entitled "Acknowledgements" or "Dedications",
   Preserve the Title of the section, and preserve in the section all
   the substance and tone of each of the contributor acknowledgements
   and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document,
   unaltered in their text and in their titles.  Section numbers
   or the equivalent are not considered part of the section titles.
M. Delete any section Entitled "Endorsements".  Such a section
   may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled "Endorsements"
   or to conflict in title with any Invariant Section.
O. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant.  To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.

You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.

You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version.  Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity.  If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.


5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy.  If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled "History"
in the various original documents, forming one section Entitled
"History"; likewise combine any sections Entitled "Acknowledgements",
and any sections Entitled "Dedications".  You must delete all sections
Entitled "Endorsements".


6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the rules
of this License for verbatim copying of each of the documents in all
other respects.

You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert a
copy of this License into the extracted document, and follow this
License in all other respects regarding verbatim copying of that
document.


7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an "aggregate" if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation's users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.


8. TRANSLATION

Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections.  You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers.  In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.

If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.


9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense, or distribute it is void, and
will automatically terminate your rights under this License.

However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
fails to notify you of the violation by some reasonable means prior to
60 days after the cessation.

Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.

Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License.  If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.


10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the
GNU Free Documentation License from time to time.  Such new versions
will be similar in spirit to the present version, but may differ in
detail to address new problems or concerns.  See
http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License "or any later version" applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation.  If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.  If the Document
specifies that a proxy can decide which future versions of this
License can be used, that proxy's public statement of acceptance of a
version permanently authorizes you to choose that version for the
Document.

11. RELICENSING

"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works.  A
public wiki that anybody can edit is an example of such a server.  A
"Massive Multiauthor Collaboration" (or "MMC") contained in the site
means any set of copyrightable works thus published on the MMC site.

"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 
license published by Creative Commons Corporation, a not-for-profit 
corporation with a principal place of business in San Francisco, 
California, as well as future copyleft versions of that license 
published by that same organization.

"Incorporate" means to publish or republish a Document, in whole or in 
part, as part of another Document.

An MMC is "eligible for relicensing" if it is licensed under this 
License, and if all works that were first published under this License 
somewhere other than this MMC, and subsequently incorporated in whole or 
in part into the MMC, (1) had no cover texts or invariant sections, and 
(2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.


ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:

    Copyright (c)  YEAR  YOUR NAME.
    Permission is granted to copy, distribute and/or modify this document
    under the terms of the GNU Free Documentation License, Version 1.3
    or any later version published by the Free Software Foundation;
    with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
    A copy of the license is included in the section entitled "GNU
    Free Documentation License".

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the "with...Texts." line with this:

    with the Invariant Sections being LIST THEIR TITLES, with the
    Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.