How to Encode & Decode Enigma Messages

[[SJ]nailz]

Following the set up your Enigma tutorial HERE (http://www.subsim.com/radioroom/showthread.php?t=162654)

Set you Enigma using this codebook entry;

http://i229.photobucket.com/albums/ee313/SJ_niall_UK/Enigma/1.jpg


Now that your Enigma is setup, we need to learn how ot use it.

The messages used here look like this;


2045/28.02.2010/U432/250/1OF1/ZAB ERA

VWFG OUGC YKII HHHJ FYQY OTPT CUXO BSQ


Lets break this down into pieces, so that we know what we have got. We'll start with the top line, or header, which is sent in plain text, not encoded.

2045 - Is the time the message was sent.

28.02.2010 - Is the date the message was sent. This must be the date at GMT, if this is wrong the message will not decode.

U432 - Is your U-boot number, or callsign.

250 - Is the length of the encoded message, not including the header, you need to count the encoded message and enter the correct number here.

1OF1 - This is part 1 of a 1 part message. This may change depending on the length of the message 1OF2 or 2OF3.

ZAB ERA - The Trigram. Getting this right is essential in being able to decode the message.


The only one of these that needs further explanation is the Trigram, this tells the decoder the last piece of information needed to be entered into the Enigma machine for it to be able to work. It is made of 2 sets of three letters.
Using the above example, the first three letters are;

ZAB

These 3 letters are chosen completely at random by whomever encoded the message, but they have an important job, once your Enigma machine has been entered with the days key, it will look like this;

http://i229.photobucket.com/albums/ee313/SJ_niall_UK/capture_01032010_025347.jpg

Set the machine with these letters, by using the changing the A A A at the top, this is our START POSITION. Like this;

http://i229.photobucket.com/albums/ee313/SJ_niall_UK/capture_01032010_025419.jpg

Using the keypad, enter the second set of three letters;

ERA

into the machine, then click on the metal tab on the bottom to reveal the true kenngruppe, or start position, for the message.

http://i229.photobucket.com/albums/ee313/SJ_niall_UK/capture_01032010_030005.jpg

Which in this case is;

RTZ

once again change the start position, this time to your decoded kenngruppe, RTZ;

http://i229.photobucket.com/albums/ee313/SJ_niall_UK/capture_01032010_030408.jpg

Then enter the body of the message on the keypad;

VWFG OUGC YKII HHHJ FYQY OTPT CUXO BSQ

to reveal the message!

http://i229.photobucket.com/albums/ee313/SJ_niall_UK/capture_01032010_030451.jpg

Tutorial by SJnailz 2010

[[SJ]nailz]

Now to encode a message.

We'll assume your Enigma is set up, and ready to rock & roll.

First lets think about the header;

time/date/your u-boot number/letters in encoded message body/parts/trigram

Before we've composed our message we don't have all the information for this, sure we know the time, date and u-boot number, but the rest we need to get.

The first thing we need to do is generate our own Trigram, again this is easy, if you can decode, you can encode.

Pick 3 random letters, any three you like! I've chosen;

SJN

Don't forget this, you'll need it later, but for now just set these as our start position on the Enigma;

http://i229.photobucket.com/albums/ee313/SJ_niall_UK/Enigma/capture_01032010_031628.jpg

then pick one of the four Kenngruppen from the codebook, for this example we're using the last day of February;

http://i229.photobucket.com/albums/ee313/SJ_niall_UK/Enigma/1.jpg

So lets enter;

GWU

Into the Enigma, this gives us a randomly encoded kenngruppe at the bottom;

http://i229.photobucket.com/albums/ee313/SJ_niall_UK/Enigma/capture_01032010_032027.jpg

DLH

Remember the three random letters we chose? SJN! put them with DLH and thats our trigram;

SJN DLH

Close your Enigma, it'll say do you want to save changes, hit yes, that way the key is set for you when you re-open it. Re-start the enigma, by now I'm going to assume you know how to set the start position of the Enigma, set it now to our chosen kenngruppe, GWU, and enter the message you need to send into the enigma,

USINGTHEENIGMAISEASY

If you click in the box at the bottom of the Enigma, you get the option to copy the encoded message to clipboard, handy!

WEDR BCWF CQWJ XJXP ORBD

This is our encoded message. Lets finish the header, add our message, and send it to BDU!

1945/28.02.2010/U432/20/1OF1/SJN DLH

WEDR BCWF CQWJ XJXP ORBD

[The Enigma]

nailz;1284983']Now that we know how to set the machine up, we need to know how to send and receive messages.


Hi [SJ]nailz,

Great job!

I'm trying to replay your decoding instructions on the enigma of U-779.
Too bad, during an air attack we needed to crash dive.
Someone forgot to close the hatch during that maneuver and a lot of
water came into the sub, making my enigma code book completely unreadable.

Can you include the machine settings in your instructions?
Meanwhile I'm gonna have a 'chat' with one of my crew.

[EDIT]
Never mind, I've found them here (http://www.subsim.com/radioroom/showthread.php?t=162654)

http://i229.photobucket.com/albums/ee313/SJ_niall_UK/Enigma/1.jpg