On the net: Encryption/notyencirp/yiptoncern/...

In a previous Despatch article I talked about email and how it works
well as a communications medium for playing games. It is much faster and
cheaper than conventional mail. I mentioned one of the advantages of
PBEM (play by electronic mail), as opposed to PBM, as being the
availability of a die roller, activated by email, that sent back die
rolls by return of email. These die rolls can be as many as are desired
and made over unusual ranges (e.g. 50 rolls of a 63 sided die). This
makes possible 2-player games as each player uses the email die roller
to generate the rolls their moves require.

The die roller builds up trust between players. Neither player can
influence the results of the die roller. What about PBMing games which
require hidden movement or simultaneous moves/orders? It is possible to
trust an opponent not to move a hidden Napoleon from one end of the map
to another. It is possible to trust an opponent who says that his move
was made in ignorance of yours. But such things can cause suspicion and
friction.

Similarly there is a problem with PBMing multi-player games which allow
secret treaties between players. In the absence of a GM (games master),
player A can deny that he ever signed a treaty with player B. And being
a GM is an unrewarding occupation. Other people get the fun of playing
the game, while the GM merely gets dumped with the administration. What
is needed in both these cases (hidden/simultaneous movement and secret
treaties) is a mechanism which builds trust between players who may
never meet.

Such a mechanism exists for PBEM. It is something that will be familiar
to all those interested in military history, encryption (also known as
code making). You must have read some of the flood of revelations about
the Allied code breaking activities during World War Two, and how these
led to vital foreknowledge of German and Japanese plans. So how does
encryption play a part in PBEM?

Let us use an example of a game that requires hidden movement. One such
is 'The Emperor Returns', a Clash of Arms game in the Zucker operational
Napoleonic series on the Waterloo campaign. In a face-to-face playing of
the game, at the beginning all the counters, representing either leaders
controlling one or more units or dummies, are inverted. They all stay
that way until the French invade Belgium. Then leaders can be revealed
if they are contacted by opposing leaders. The detailed make up of
forces controlled by leaders is not revealed until combat takes place.
This is somewhat difficult to achieve fully face-to-face as an
inadvertent peek at an opponent's organisation sheet can reveal what
units make up what leader's force. It seems impossible to achieve in a
PBM. But not so in a PBEM.

The solution is for each player to send the other the complete
organisation sheet for his forces. To prevent his opponent reading this
sheet it is encrypted (coded) prior to sending. So each player ends up
with his organisation sheet in readable form and a copy of his
opponent's sheet but encrypted. As the game progresses and units change
hex position, strength etc, updated organisation sheets are sent to the
opponent in encrypted form. Leaders and units are revealed as normal as
the game progresses. At the end of the game each player sends the other
the 'key', the password or pass-phrase which decrypts (decodes) all his
organisation sheets. Thus it is impossible for either player to cheat,
because if Napoleon is 'nudged' across the map then this will be
revealed in successive editions of that player's organisation sheet,
which can be checked by his opponent at the end. Cheating is thus prevented
by the guarantee that it will always be revealed at the end. The
movement is actually more 'hidden' than in a face-to-face game, as
peeking at an encrypted organisation sheet requires that you know how to
decrypt it.

Trust thus hangs on the strength of the encryption routine. It must be
easy enough for ordinary mortals to use to encrypt text but tough enough
to stop efforts to prematurely decrypt it. This rules out paper and pen
based systems using simple letter transpositions (e.g. shift all letters
5 to the right, so that A becomes E, B becomes F etc). Software is an
excellent tool for encryption. You may know that most word processors
will store text in encrypted form using a password that you enter. You
not know that there exist programs available from the Internet that can
decrypt that text! However there is one piece of software that is freely
available that can encrypt so well that even code breaking experts
cannot break it: it is called Pretty Good Privacy (PGP) and is available
from the Internet (as well as other places). PGP is so good at
encryption that its widespread use is worrying certain governments who
fear that it makes private communications between individuals
untappable.

Here is an example of a piece of encrypted PGP text: it is the current
hex position and force composition of Napoleon in my current PBEM of The
Emperor Returns:-

- - -----BEGIN PGP MESSAGE-----
Version: 2.6

pgAAASEjsBGaxgQqBYNQ9NK0B8cS4OiyF3gTnRbl1RSYb0eSpZ6w9sCxJ2/Xln2M
p8NpBMBd11NNzSOzVs+ppHcB2gblfl1Z3rdaq0QNN4DdXnYGvAIeYZ3Gpcond6TL
cs9O8+K9SFcmThwIVFqFdMlko+O0gQSDwcZHhaspC3I2CHJCLAekqrm5Qjqk0Lbl
eeEd23Qpm1r9zoiQ+42GiQYkrdMgdGuHLvb71lXSF0F6hixOdbzjTVye6EFp2TUH
hh7wc9WE6+DANnGx9iaF6WAtFgW34eNusjQ1WvO5EhfqhPMb9oUXgfSw8uha1unq
tjeJ4CGVHDUhpTPhf28O8JePX0iTdk5Rggn8zBJS79Gt0makxUnbZPZx9ygS0EpQ
HiMGncYK
=Qrj4
- - -----END PGP MESSAGE-----

A year's supply of beer to anyone who can tell me the exact hex position
of Napoleon and the make up of his force!

Encryption can be used for simultaneous actions or movement. For example
in 'Nicaragua', an S&T game on the revolutions in that country, combat
involves simultaneous declarations of type (either conventional or
guerilla) by the two sides, government and rebel. In a PBEM the
government player sends their choice encrypted. The rebel player, on
receipt of the encrypted choice of the government player, sends their
choice in ordinary text. On receipt of this choice, the government
player sends the rebel player the password to decrypt his choice. It is
not possible to send one password for one choice and another password
for a different choice, so the government player cannot alter his choice
after knowing the revel player's choice.

Encryption can also be used for hidden picks. For example, in the
Victory Game 'Civil War', each side, Union and Confederate, picks from a
pool of inverted leader units when leaders are brought on. To do this in
a PBEM each side makes a list of all their leaders in the pool and then
puts the leaders on this list into a random order. The leaders are then
numbered. An encrypted version of this list is sent to the opponent. A
leader is then drawn by die rolling (by email using the email die roller
mentioned above) a number to identify one of these leaders. Leaders are
known by their numbers until revealed. At the end of the game players
exchange passwords for the encrypted leader lists so that each can see
that Confederate leader 23 really was Lee and Union leader 43 Grant.

Recall that I mentioned earlier the need for a GM to run multiplayer
games PBM. These often require that the GM handle things that certain
players should not have knowledge of (like a secret treaty between other
players). Encryption can help out here too. Firstly it can dispense with
the need for a GM.

I am the 'player-GM' in a PBEM game of 'Conquistador'. I am playing the
German Banker and also GMing the game, i.e. I am responsible for working
out the results of player orders. My orders as player-GM are encrypted,
and sent to all other players prior to me receiving their orders. This
stops me from knowing other player's orders before writing my orders.
The encryption stops other players knowing my orders before they write
their orders. I circulate the password to decrypt my encrypted orders
when I have received all the other player's orders. All orders for a
round are be published for all players to see, including the decrypted
text of my orders. It is incumbent upon the other players to decrypt and
check the encrypted orders I circulated first against the text version I
circulate later. Not all the other players have to be able to decrypt
the player-GM's orders (although at least one player should be able to,
to keep the player-GM honest). All die rolls are generated by me using
the email die roller mentioned earlier. In this way a multi-player game
can progress quite happily without a GM. The player-GMship can be passed
around the players, so sharing the load of running the game. If a
player-GM drops out the game does not fold, as would a traditional GM'd
game.

Secondly encryption can allow players to sign secret treaties that can
be validated later on by players who are not a party to the treaty. The
mechanism for this is the use of 'digital signatures'. A digital
signature is a string of characters (see the example at the bottom of
this article) which identifies the author of a treaty and also serves as
a check that the text of the treaty has not been changed. How is a
digital signature generated?

Each player needs to use special encryption software (like PGP mentioned
earlier) to generate two 'keys', one called the 'public key' which can
be published far and wide, the other called the 'secret key' which must
not be revealed to anyone. These keys form a linked pair, although
knowing the public key does not in any way give knowledge about the
private key. I think of the public key as being a bank account number
and the private key as the account's PIN number. My public key looks
like this:-

- - -----BEGIN PGP PUBLIC KEY BLOCK-----
Version: 2.6

mQBNAi0KAbAAAAECAKvbAmNHUAltz0+5Aeol24zINIzrqFBzx68MP61EKgGXPJLf
61O3HjfgnkN6bFGbJbLMajbyByOm7kIz2ig3eJkABRG0IkFsYW4gUG91bHRlciA8
YS5wb3VsdGVyQGx1dC5hYy51az4=
=M5dE
- - -----END PGP PUBLIC KEY BLOCK-----

A digital signature, like the one below, is made by using your secret
key on the text to be signed. Anyone else, using your public key,
because it is linked to your private key, can then check your digital
signature. It sounds like voodoo, and the mathematics which prove the
security and validity of its operation are truly complicated (I make no
pretence to understand them) but it does work. All you have to do to
believe me is get a copy of PGP, give it my public key above, the text
of this article and the digital signature following and PGP would tell
you I wrote this.

If this all sounds fiendishly difficult and time consuming, remember
that it is all done by computer. A by product of all this is that email
is potentially the most secure form of communication around, if you use
encryption. If you suspect your postman of being in league with your PBM
opponents then start PBEMing instead and use encryption!

-----BEGIN PGP SIGNATURE-----
Version: 2.6

iQBVAgUBLvxHeu5CM9ooN3iZAQFzowH/Y4ZZjrvJ3IdtPCh996mWxCZTY3eMKc4Q
Mcy6J7WkjieMQ/8Ryc7/R2wkpckRyjEYGi0qhmNClCCa2nzV+8Uqbw==
=aKNr
-----END PGP SIGNATURE-----

Alan Poulter

Originally published in EuroDespatch: AHIKS Europe Newsletter, Vol.1 No.1