Enigma was a musical experiment created by Michael Cretu. He took a lot of samples from various sources, mixing them into a very ethereal sound with some very nice beats.

Extremely popular over in Europe, and pretty popular here, though it doesn't get much airtime. The first album, MCMXC A.D. was on the Billboard charts for about 4 years.

It can be classified (though not well) as somewhere between ambient music and new age.

Albums:

The Enigma was a mechanical cipher system created around 1918 and produced by Scherbius & Ritter, a German engineering firm. It was invented by Arthur Scherbius to replace the pencil and paper cipher systems used during WWI with machines. The company produced both a commercial version and a millitary version. The millitary version was designed to be stronger than the commercial version.

This machine consisted of a number of components. At the highest level it is comprised of a keyboard to enter the plaintext, a scrambling unit, and a display board. The scrambling unit contained several wheels that performed most of the scrambling. The scrambling wheels had wiring on them. They were like very short cylinders or disks that had electrical wiring to take electric currents from one side of the disk to the other. These paths did not head straight through the disk, they wound around through the disk and exited at some other point on the opposite side. Each wheel had a different wiring scheme. The wheels sat one after the other and the current would pass through all three disks. But this would still basically be multiple simple substitution cipher which is no stronger than a single simple substitution cipher. To make the cipher better the first wheel turns one position after each click of a key on the keyboard. The second wheel rotates one position, after each full revolution of the first wheel and so on. Doing this makes the engima machine a polyalphabetic substitution cipher. But this still wasn't good enough, a stationary reflector was added after the wheels to reflect the signal back throught the three wheels along another path. At this point we have the current being send by a key pressed on the keyboard through the wheels, through the reflector and back through the wheels along another path, and finally lighting a letter on the display board.

This still wasn't deemed good enough either, so they also added a plugboard that allowed the operator to set up a simple substitution between two letters using a cable. This plugboard was placed between the keyboard/display and the rest of the scrambling unit. With several cables you could substitute several letters. Now we have the signal going from the keyboard throught the plugboard, through the scrambling wheels, through the reflector, back through the scrambling wheels along another path, back through the plugboard, and out to the display. This is the basic construction of the Enigma machine used by Germany during WWII. The original design had three wheels in use, a later version contained 5. Jetifi tells me the original version also contained a plugboard with a default A to A mapping

Wait there is more. The wheels could be placed in any order. And while you could only use three (or five) wheels at one time you could have additional ones that could be swapped in also. The German code books contained the primary settings of the Enigma for a given day, which included which scramblers were used, in what order, in what starting position, and what letters were swapped on the plugboard. To make messages even harder to decrypt only the beginning of a german message were encrypted with the day settings specified in the code book. This beginning contained three letters that told the operator how to set the wheels for the rest of the message, intially these three letters were repeated once. So the first six letters of a message in plaintext might have been HJUHJU. Which after decrypting this beginning block with the day's settings the operator would reset the first wheel to H, the second to J, and the third to U and decrypt the rest of the message. (obviously the five wheel version had five letters instead of three). This meant that of all the german messages the Allies captured they only had very small pieces of ciphertext encrypted the same way. Note the repetition, and remember that any repetition is the downfall of any encryption scheme.

For more info see
http://www.attlabs.att.co.uk/andyc/enigma/about_enigma.html
http://www.gl.umbc.edu/~lmazia1/Enigma/enigma.html
An applet that simulates the Enigma
http://www.attlabs.att.co.uk/andyc/enigma/enigma_j.html
Part of the Everything2 Crypto Project.
Enigma is a performer with the Jim Rose Circus and has also appeared in television, most notably in an episode of X-Files. He is tattooed as a jigsaw puzzle from head to toe and at the shows he displays his weird eating habits by eating things like maggots and cockroaches. He eats things that other people normally wouldn't even touch. He has also taken over the act from The Tube, who has left the group, where he drinks his beer twice after having his stomach pumped (bile and all). The Enigma is married to tattoo artist Katzen who tattooed all of the lines working six hours a day and every day for a month. Over 100 tattoo artists have been involved in filling the puzzle pieces. Every single puzzle piece will be blue all the way up to the eyelids when its complete.

The Enigma has also got implants into his scalp. The implants are made of teflon, creating two small horns on his forehead. The plan is to replace the teflon implant after a while with new implants made of coral. These implants are expected to grow into his skull and through his skin creating even bigger and more natural looking horns.

And you thought you were weird...

The main weaknesses of the German Enigma system were:
  • It never encrypted a letter to itself (due to the way the reflector sent the signal back through the disks along a different route)
  • It was encrypting German (a very structured and predicable language with large words made up of smaller words 'nailed together')
It was quite often possible to predict the presence of a particular word or phrase in a message (the plaintext). The code breaker then looked for a sequence in the ciphertext where none of the letters matched. This was the start of the code breaking process at Bletchely Park. They then used machines (called "Bombe"s - thanks merlin83) to search for a configuration that gave that translation.

Once they had broken one message for that day they then had that day's key that would allow them to decrypt other messages.

Part of the World War II Cryptographic Simulation

German point of view:
The primary encryption device for the German military is the standard, three wheel, Enigma. In addition to this different branches of our military and government use variations on the basic Enigma. Our navy uses a four rotor variant with eight standard rotors, 2 'gamma' and 'beta' rotors and different reflectors from the standard enigma. In addition to this there is the Abwher Enigma which does lacks a plugboard but compensates for this with heavily notched rotors.

The Enigma works on the same principle of rotors developed by Edward Herbern of the United States. The machine uses a series of 'rotors', which you can think of as gears, to heavily scramble a message. Each rotor has 26 contacts, each representing a letter of the alphabet, on one side. These contacts are then connected in a scrambled manner to another contact on the other side. Here is the wiring used in the first rotor of the Enigma:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

E K M F L G D Q V Z N T O W Y H X U S P A I B R C J

So the effect is that if the contact for A receives a 'live' current it is then transformed to the contact for E. This is the basic principle of monoalphabetic substitution that has been used for centuries. The Enigma takes this to an incredible degree of complexity. It uses three regular rotors to perform substitutions as above, and a reflecting rotor that sends it back through the first three rotors again. By itself this would offer very little security. What makes the Enigma so secure is that on each key press the first rotor rotates. When the first rotor reaches it's 'notched' position the middle rotor rotates and so on. This means that when the first rotor is in the 'B' position, the letter sent to the 'A' contact is received at the 'Z' contact, an offset of 1. A simple change such as this completely changes the route the current takes, resulting in a wildly different encrypted letter. The 'alphabet ring' on the outer side of the rotor can also be rotated, this is called the 'ring setting'. If this was rotated forward two positions it would mean that when the rotor indicator reads 'A' it in fact mean 'Y'. In addition, changing the 'ring setting' would also change the position of the notch.

In addition to this basic rotor encipherment, the military Enigma has two additional features which make it quite safe. Once the current goes through the first three rotors it is transformed one more time by a 'reflecting' rotor and then sent backwards through the first three rotors. There is also a 'plugboard' on the bottom of the machine that the current goes through both before and after the rotors. The plugboard has 26 different plugs, each representing a letter of the alphabet. The operator can connect these plugs together with a standard set of 10 wires. If the letters 'D' and 'H' were connected and the operator typed a 'D' it would first be transformed into an 'H' before continuing to the rotors. In addition, if the rotors produced an 'H' it would be transformed into a 'D' before going to the lightboard.

As an example. if the letter A were typed:
A -> plugboard
On the plugboard A is connected to D so the current is changed to D
D -> rotors
Now, before going to the first rotor the offset of the rotor must be compensated. If the rotor is at the 'C' position then the input will arrive three positions before.
B -> rotor 1
Rotor1 scrambles it, it is then adjusted for the offset of rotor2
Rotor2 scrambles it, adjusted for rotor3
Rotor3 scrambles it, adjusted for reflector
reflector scrambles it, adjusted for rotor3
rotor3 scrambles, adjusted for rotor2
rotor2 scrambles, adjusted for rotor1
rotor1 scrambles, adjusted for output
If we now have the letter 'A' it then goes through the plugboard one more time and comes out as 'D'

Messages can be decrypted by simply typing in the text with the same settings because the reflector makes it seem that the message is being forced back the other way.

The Enigma is operated by first consulting a keybook for the daily key. This specifies the rotor order (the order the rotors are put in the machine) the ring-settings of each rotor and the plugs that are to be connected. The operator then types a random 'indicator setting', changes his rotors to that setting, and types the rest of the message. The receiver can then decipher the first three letters and change his machine to the same settings to decipher the message. At the beginning of the war we enciphered our indicators twice; however, we soon quit this practice realizing the advantage it would give an enemy.

United Kingdom point of view:
The Germans use a variation on a commercial machine called the Enigma that was sold prior to the war. They have developed their own rotor wirings and, most importantly, implemented a 'plugboard' that provides a great deal more protection. Hitler and his commanders believe that this system is unbreakable. They are wrong. Before our Polish comrades fell at the hands of the fascists in 1939, they had broken the Enigma. Seeing their downfall approaching, they sent us their work. Where we had previously failed, the Poles succeeded. They recreated (reverse engineered!) a military Enigma from their knowledge of the commercial machine and encrypted messages. They built an electric-mechanical device, that they called a 'Bomby' (probably because of the ticking sounds they made,) to figure out the daily settings of the Enigma. We took this work and flew with it. Our headquarters in Bletchley Park is now generating sheaths of daily intercepts, called ULTRA intelligence, that has benefitted our war efforts beyond measure.

Perhaps our greatest cryptologist, Alan Turing, has taken the Polish bomby to a new level with the Turing bombe. This machine relies on the mathematical principal of reductio ad absurdum. Essentially the machine tests every possible rotor setting to see if it will generate a given cipher text from a given crib of plaintext. Each time the machine reaches a situation it thinks can generate the necessary plaintext, it stops all activity and produces a 'drop'. This drop is then recorded by a technician, tested, and (if false) the machine will continue to run. The plugboard on the Enigma further complicated things, producing a large number of false drops. Fortunately, another one of our cryptologists, Gordon Welchman, has developed an addition the the Turing Bombe called the 'Diagonal Board'. The Diagonal Board contains an array of 26 plugs by 26 plugs. This allows each drop to be tested against all possible plugboard combinations to see if it is accurate.

The bombe operates by using 60 groups of 4 disks each. Unlike the real Enigma, each disk has two concentric rings of 26 contacts, one for forward encryption and one for backward encryption. This was because the Bombe needed to test the electrical state at each point of encryption; one set of contacts operating for both sides of encryption would not work. There are 60 groups for the 60 possible combinations and positions of the five availailable rotors in the standard Enigma. Each offset and ring setting is then checked until a working drop is delivered. To go through all the possible combinations the machine usually takes 12 hours.

Allied Crytographic Success


Introduction

The Enigma machine was a sophisticated mechanical cipher invented in around 1918 by a German engineering firm. It was intended to replace the easily cracked ciphers used during the First World War with something more difficult to decode, and to this end, the company produced a more complicated military version.

Many cryptographists would agree that the inter-allied intelligence operation Enigma was the greatest success of World War II after the atom bomb. The breaking of this sophisticated German machine cipher was probably the most spectacular event, in terms of its difficulty and far-reaching consequences, in the entire history of cryptography. Operation Enigma was one of powerful weapons of the anti-Nazi war coalition but in contrast to that of nuclear weapons, which itself had come to light in the terrific holocaust of Hiroshima and Nagasaki in August, 1945, the secrets of the Enigma remained hidden and unknown to the public for the next almost three decades. Its details have started to emerge only recently after the Official Secrets Act has ceased to apply.


Encrypting Messages in Enigma

Each day, a new three letter key was chosen and distributed to the German Enigma operators. This told them how to set up their machines in order to send and receive messages on that day. As an added security measure, the operators would often only use the day key in order to encrypt and send a new message key to another receiver. This key would then be used to encrypt messages sent between the pair as normal. In order to avoid transmission errors, each message key was sent twice.


Why were Enigma Messages so difficult to decipher?

Although the design of the Enigma machine was simple, it exploited the rapidly increasing complexity which arose from only a few operations. For instance, the plug board consisted of six cables each of which swapped a pair of letters around. Due to the fact that there are about ten million ways in which six pairs of letters can be chosen from twenty-six it became impossible to decipher Enigma messages by brute force.


How was the Plugboard Bipassed?

In order to successfully decipher the messages it was necessary for Turing's team to find messages which, while being different for each scrambler setting, would not be affected the exchange of the plugboard leads. The point that could be most easily exploited was the fact that the message key would be repeated twice at the beginning of each transmission. As a result of this it it was clear that the 1st and the 4th letters of each message, before encryption, would be the same, as would the 2nd and the 5th and the 3rd and the 6th. From this it could be seen that a particular letter which might be encrypted as an F initially would be encrypted as an M three letters later. If enough messages were intercepted then tables such as that shown underneath could be built up.

A B C D E F G H I J K L M O N P Q R S T U V W X Y Z 

S V N G Y P Q T E B L Z J R U D F C M O I X H K W A 

From such a table chains of letters could be created with varying numbers of links. For the example above there are three chains.

ASMJBVXKLZA (10 letters)

CNUIEYWHTORC (11 letters)

DGQFPD (5 letters)

For each scrambler setting, the number and length of the chains would be different but unaffected by the plugboard settings. Hence, all that had to be done was to compile a file of all the scrambler settings and the corresponding chains. Each day, the scrambler settings could be looked up and the day key determined.

Visit this site: www.ugrad.cs.jhu.edu/~russell/classes/enigma/ to use an online Enigma Machine

Ed. note: The Enigma simulator has been moved to http://russells.freeshell.org/enigma

Enigma : The hacking that won the war

What it was

The Enigma was the cipher encoding that the Nazis used during the second world war

Types of Enigmas

  • Civilian Enigma (3 wheels + plugboard)
  • Army Enigma (3 wheels + plugboard)
  • Navy Enigma (3 wheels + plugboard)
  • Airforce (Luftwaffe) Enigma (3 wheels + plugboard)
  • Shark Enigma (4 wheels + plugboard)
  • Italian Enigma (3 wheels)

How it works

(the previous nodes pay some closer attention to how the Enigma works)

The Enigma is a machine that looks like a typewriter. It is an electronic device that has three cipher wheels in it. When the operator sets the wheels and presses an "A" on the Enigma, a bulb marked with the letter "T" might light up on a board. The letters that are keyed in are not transmitted - instead, the "converted" text is sent via morse.

When pressing a key on the keyboard, electric current would move via the three cipher wheels and scrambling circuitry. The Enigma had to be set up by turning the wheels to an agreed setting, and by plugging connectors into specific sockets.

So far, there hasn't been much encryption going on. Here is where the fun begins; the right wheel revolved counter-clockwise a twentysixth of a revolution (i.e one letter) every time a key was pressed. This means that writing the string "AAAA" might come out as "FEYW". Not only this, but there was a complicated system of the wheels turning. When the right wheel had made a full revolution, for example, one of the other wheels would turn one notch. Scientists have calculated that if using the Enigma as a regular typewriter (i.e without changing the settings underways) - there would be in excess of 17.000 keystrokes between every time the wheels being back in their original position.

Inside the Enigma, there were three (four, in the Shark Naval enigma towards the end of the wars) wheels with 26 pins in each. These pins would connect with the next wheel or the "switchboard" at the end of the current.

Each of these wheels contained 26 wires, so that if the current could take the following route:

  • Operator presses A
  • Wheel 1: A -> T
  • Wheel 2: B -> W
  • Wheel 3: Q -> B
  • Switchboard E -> Q (also called reflector)
  • Wheel 3: T -> R
  • Wheel 2: N -> P
  • Wheel 1: L -> Y
  • Light: Y

For a closer look on how all of this works, read how to make an enigma

Why it was crucial

Breaking codes today might seem boring, if not trivial to most of us. In wartime, however, the situation is very much different. In wartime, positions of submarines, battle ships and aeroplanes is crucial. Also, most invations and attacks don't happen spontaneously - they are all carefully planned. this is where radio and Morse code comes in.

An old saying says "Keep your friends close and your enemies closer". This is not without reason - knowing what your enemy is going to do before they are going to do it might win you a war. This is what the Enigma cipher was all about. From before the war even started and all the way until D-day, when allied forces set foot on Normandie in France, the Enigma cipher was a constant battle.

The breaking of the Enigma cipher has saved the lives of thousands and thousands of allied sailors, and the fact that the allied forces often knew where the German submarine packs would hang around, meant that the tanks, artillery and other weapons coming across the Atlantic from USA and other countries reached their destinations.

How it was broken

Before the war

In 1931, Hans Thilo Schmidt, brother of a high ranked German army official, and trusted employee of the german cipher office, sells information about the Enigma to french secret service - manuals on how to operate it and the current settings of the machine. The information was sold to the French secret service, who were extatic about this breaktrhough.

Between 1931 and '38, more and more documents about the Enigma were leaking from the cipher office. However, the non-technical documents and current settings of the cipher machine were not believed to be able to help crack the code.

When rumours about the plans of invations by the Germans started moving, several instances started work on trying to break the Enigma codes. A team of Polish cryptographers, led by dr Antoni Palluth, were on the task from 1932.

The German Mistake

When sending a message, the Germans decide d to send the settings twice, before sending the actual message. If you know anything about cryptography, you know that was a big mistake;

Sending the settings would be done in a predetermined setting, say "BLT". If the message would be transmitted on in the wheel settings of "QWE", the operator sending the message would first set his machine to BLT, and then type QWE twice. The result would be something like "RHU TFP". When the receiver gets the RHU TFP message, all he would have to do is to is to set their machine to BLT and then type RHU TFP. The bulbs lighting up would then be "QWE QWE".

The receiver would then set his Enigma machine to the QWE setting, and decode the rest of the message.

The problem with this, of course, is that when the Britons found out that the first 6 characters of the message would be the same sequence repeated twice, this helped them in their quest. Because the manuals had been captured, the fact that the current went through the machine twice, and that the codebreakers knew that the characters were in the pattern "ABC ABC", led them to discover ways to interpret the first 6 characters. Doing this, they could decipher messages relatively fast - usually within 48 hours.

This procedure was changed in 1938 (random letters were sent before the actual message and acknowledgement) but the practice of sending the cipher settings twice continued - allowing the code to be broken again, except it now took some more time.

The second world war

As the second world war broke out, the Germans started making more code wheels. There were still just three wheels in use, but now a total of five wheels were available. Also, considering that each wheel could be placed in any position in the machine, and each wheel had 26 possible positions, you now had a machine with (5*4*3*26^3)

It was not until December 1939 that the Enigma messages could start to be decoded.

Earlier, the codebreakers had discovered that there was a certain pattern to the messages, and devised a system of perforated sheets of paper. A certain result from the first six characters of the message ruled out a load of options - another result ruled out even more etc. The problem, of course, was that the sheet system only worked for a particular set of wirings. If a different order of wheels was used, the sheets were useless. In the beginning there were just three wheels, making 6 different possibilities when it came to wheel order (3*2*1) Later in the war, possibly when the Germans realized that the code had weaknesses, two extra wheels were introduced. Because there were 60 possible combinations now (5*4*3), the codebreakers would need 60 sets of sheets. This was not a good solution, and a new way to break the codes had to be found.

In mid-January 1940, the first "genuine" wartime message was decoded.

Historic points in the breaking of the Enigma code

Alan Turing is the man who has become most famous for the breaking of the Enigma. The first important thing he made was the Bombe. This was an electronic device that had several Enigma machines wired together. The purpose of this was to rule out combinations of wheels and positions, much like the sheet system, only more automated. This original idea was later improved a number of times, and it is believed that this invention is what made the decryption possible at all.

The Navy Enigma was different from the other two, as the Germans felt that the war on sea was the most important to begin with. Indeed, the German wolfpacks (submarines) were a major danger to ships in the Atlantic and North Sea. This was also why the codebreakers tried hardest to break the Naval Enigma. The first time the Naval enigma was actually broken was on April 25th 1940. Unfortunately, the Germans kept changing their codes, and every time a code was changed, the work with breaking the Enigma started over.

The British codebreakers had a lucky break when they discovered a severe weakness in the German coding procedures: When sending weather forecasts around, the Luftwaffe Enigma was used. However, there was a consistency in how the messages were sent; They always begun with something like "Station Oslo reporting". Knowing this, the Brits could automate the tasks of breaking the codes by using the Bombe, and by looking for the message "Station (...) reporting". Because the breakers would usually know where the messages came from, breaking the code became a fairly easy routine task.

From August to October in 1940, the codebreakers couldn't decipher one single naval Enigma message, as there had been a slight change in procedure, making the decoding more difficult.

In May of 1941, Allied ships managed to capture the German submarine U-110. This marked a major breakthrough, as it was the first time the codebreakers had their hands on an original submarine Naval Enigma machine, and copies of all the codebooks that were needed.

From July of 1941 all the Naval Enigma messages were broken. Some of them took a litttle longer than others (up to a week) but most of them were broken within 48 hours. When the code was broken, the codebreakers could quickly decrypt the remainder of the messages for the 48 hour period, until the codes would once again be changed.

In 1942, something bad happened - The Naval Enigma was suddenly unbreakable again; The original Naval Enigma had been switched with what the Germans called the Triton Enigma (the codebreakers at Bletchley called it the Shark Enigma). This was the same as the original enigma, but with another wheel added to it. Fortunately, this wheel was fixed in the machine and did not add up to the total number of wheel orders. On the other hand, this did multiply the number of possible ciphers with 26 - making the use of the Bombe more time consuming.

Chronological overview

  • 1931
  • 1932
  • 1937
    • The Germans change their Enigma indicating system, and the Polish can't read the messages anymore
    • A message is intercepted in France, almost revealing Schmidt's spy role.
  • 1938
    • The Germans change their Enigma procedures, making it impossible for the Polish codebreakers to read the messages
    • The polish develop a Bomby, which became the idea for Turing's Bombe later on.
    • The Germans start using two extra code wheels on their Army enigma. The Polish cryptographers cannot break this code anymore.
  • 1939
  • 1940
    • January: First wartime Enigma messages are broken.
    • February: Two extra code wheels that are issued to Naval Enigma operators are captured from a submarine
    • March: Turing invents the Bombe
    • April: First wartime Enigma message is broken within 24 hours of being sent
    • July: Bigram Tables system is included in the Enigma procedures - makes it impossible to continue using the old methods for breaking the code
    • September Ian Fleming comes up with a crazy plan to capture codebooks: Operation Ruthless
  • 1941
    • March: A german trawler is captured in Norway. The trawler has the settings and charts needed to be able to read the Naval Enigma, even with the Bigram Tables
    • May: A german weather ship is captured in the north sea, with new codebooks
    • May: The U-110 submarine is captured, making it possible to read offizier messages
    • June: The germans start suspecting that the Allied forces are reading the Enigma messages
    • June: The germans start using new bigram tables
    • November: The germans, once more, start using new bigram tables
  • 1942
    • January: The weather stations now use a separate codebook, making it impossible to use the weather stations as a "back door" into the Enigma settings
    • February: The Shark Naval Enigma gets introduced; adding a new reflector and another code wheel
    • December: The Shark Naval Enigma is finally broken
  • 1943
    • February: The codebooks are being replaced
    • March: The codebreakers find a way to break into the Shark Enigma again
    • September: Hans Thilo Schmidt commits suicide, before the germans find out how much information he has leaked to the allied forces
  • 1944
    • The Enigma gets broken a few times, and then is closed up by the germans. Again and again :)
    • June: D-day, Germany goes down.

 

The Enigma Metanode

  • Codebreaking tools & Techniques

Sources and Comments

The base of this writeup is the book Enigma: The Battle for the Code written by Hugh Sebag-Montefiorte. If you are interested in reading an engaging, well written and seemingly complete account of what went on when the Enigma was broken, this would be the book.

Other sources include a selection of sources from the internet and history books (particularily Seizing the Enigma, by David Kahn, as well as the play Breaking the Code, written by Hugh Whitmore.

There is really no way to tell the whole story about the Enigma without doing a lengthy study on the topic. This writeup becomes a mere shadow of the complexity and excitement, but I believe it makes a good overview of what went on and why.


-30-

CRACKING ENIGMA

Introduction

Everyday the enigma codes were encrypted using a new day key these keys were distributed to all the German operators to tell them how to set up their machines at the start of each message. For even greater security the operators would use the day key to encrypt a message key then both the receiving and the transmitting operators would set their machines to the message and then encrypt the message as normal. However in order to avoid any radio transmitting mistakes they had to send the message key twice. The message key consisted of three letters these letters represented the starting letters on each scrambler.

How it was done

The main reason that it was impossible to simply try every possible starting combination and see which one worked was the plug board the plug board consisted of 6 cables which swapped 6 pairs of letters around and because there are several million ways in which 12 out of 26 letters can be swapped round checking them all was impossible.

What the English needed was something that would be different for every scrambler setting but would be un affected by swapping letters round. So used the fact that the Germans repeated their message keys. They knew that the 1st and the 4th letters of each message was the same in the plaintext as were the 2nd and the 5th and the 3rd and the 6th. From this they could work out that a certain letter, which might be encrypted as A, and three letters later the same letter might be encrypted as E. Then they could make tables showing what certain encrypted letters became three letters later; with enough messages complete tables could be made.

e.g.

A B C D E F G H I J K L M O N P Q R S T U V W X Y Z

E D W T R Q Y U I O P A S F G H L Z J X K C V M B N

From a table such as this you can construct chains of letters in this case you would start at A go down to E go to E on the top line down to R and so on.

AERZNGYBDTXMSJOFQLA 18 links

CWVC 3 links

HUKPH 4links

II 1link

For every scrambler setting the number and length of the chains was different and they were unaffected by swapping letters round so all the English had to do was compile a book of all the scrambler settings and the corresponding chains and then just work out the chain lengths everyday and look up the scrambler settings for that day. Once they knew the day key they could work out the plug board settings with comparative ease by looking for phrases that made sense when a pair of letters was swapped for example.

Allive in Belrin

could be

Arrive in Berlin

with the R and the L swapped round. Once the plug board settings had been guessed all the messages that day could be deciphered and at midnight the process would start again.

"This is our bloody war in here, you see. Beep beep bloody beep."
- one of the radio opperators at Bletchley.

Enigma
(the 2001 movie based on the novel by Robert Harris)

Historically, the film starts just as the Shark (German submarine 4-codewheel naval enigma) cipher is introduced.

Lots of references to technical enigma references for the codebreaking buffs among the moviegoers, but probably (this was confirmed by a friend of mine) not too advanced for the "average joe".

In this film, a lot of exciting moments and fascinating facts about the breaking of the enigma cipher must leave way to a rather uninteresting and uninspiring love story, which gets blown completely out of proportion. Okay, perhaps it is a problem that one of the lead codebreakers had a bit of a broken heart, but it isn't exactly as if Tom Jericho was the only codebreaker at Bletchley Park.

Even worse, however, the key plot in the movie - the love story leading to a spy leak wrecking Bletchley's codebreaking efforts - seems to flatout contradict everything history dictates - including the writeup by SharQ above.

The story further focuses on a few events throughout the research for the enigma. among other things, the movie shows the dramatic exchange of hundreds of lives and a dozen merchant ships for the new Shark submarine enigma. When the enigma codes were changed by the germans, along with the introduction of a complete radio silence, the only possibility was to use the short message book (of which the codes had not been changed) which the packs of submarines used as guidance when chasing down the merchant convoys.

The Verdict:

I would say that the movie certainly is worth watching: It is a rather entertaining film - The costumes are gorgeous, the car chase is a bit over the top, but nevertheless exciting. The storyline is not entirely historically correct, but the paranoia, the tension and the gravity of the war has most definitely been illustrated in a most convincing way. Never mind that they have turned it into a bit of a detective story, and that the lead role's name is Tom Jericho rather than Alan Turing.

Starring: Dougray Scott, Kate Winslet, Jeremy Northam, Saffron Burrows, Claire Romilly, Nikolaj Coster-Waldau

Directed by Michael Apted, Screenplay by Tim Stoppard, Based on the novel by Robert Harris.

Enigma is a GNU game available in Linux distributions. It is available to Debian as an APT module. It is a hybrid of Oxyd, Sokoban, Marble Madness with a dose of Harry Potter thrown in.

Oxyd

The objective of each level (apart from the meditations, see below) is to find and visit all the oxyds on the level. Oxyds are square blocks which light up with a colour when touched, but sometimes, you will find blocks which look like oxyds but aren't. There are always an even number of oxyds - pairs of each colour. You need to visit both members of a pair in succession, when they will stay lit. Touching a different coloured oxyd will reset an unmatched one which is lit.

You have control of a black marble, and three lives in which to complete the level (but sometimes a software setting only gives you a single life). You push the marble using the mouse, and can pick up objects lying in the grid by moving onto the squares where the objects are.

The bottom display shows your inventory of up to 12 objects, including spare lives you haven't used. Right mouse click cycles the inventory. Left mouse click uses or drops the leftmost object in your inventory.

Some levels don't have oxyds, but are meditations. Instead of controlling one black marble, you control 4 white balls, simultaneously. The idea of these levels is to get all four balls into designated pits at the same time.

Sokoban with Newtonian Physics

Whereas Sokoban itself is an abstract puzzle based on a finite sequence of moves, Enigma's version involves using your black marble to move the blocks. These blocks are hit rather than pushed, resulting in a recoil. This recoil could result in you unintentionally pushing back another block behind you.

There are also a variety of different floor surfaces, with different frictional characteristics. These include ice rinks and space (where you get no control of your movement at all, continuing according to Newton's First Law of motion). There are also inverse floors where you move right to go left, up to go down, etc. Some floors have slopes, others lethality if you stay in one place for too long.

Many levels have water, which is lethal (your ball can't swim). But you can build bridges by pushing special wooden blocks onto the water.

Lasers

Some levels have laser beams, for which the beam itself is lethal, but usually useful serving some other purpose: illuminating an oxyd otherwise unaccessible, or morphing objects in its path. There are also prism and mirror blocks, which can be pushed and rotated to divert the beam.

There are a variety of controls, which can do things such as turning on or off a laser, opening or closing a gate, etc. These include triggers, switches, key locks and coin slots.

Summary

The hundreds of levels that come with the distribution provide a wide range of puzzles, mazes, obstacle courses, tight ropes and other challenges, some of which are extremely difficult bordering on the impossible. For the complete enthusiast, it's possible to create your own levels - the game is open source, and there is an active mailing list for developers.

There's no save function, for persisting your ball mid-level, which is a shame for the more difficult levels. Many an hour has been wasted trying to crack these levels, nearly successfully, only to make a ridiculous mistake at the end.

I've found some bugs in the game. Some levels which refuse to load, freeze up, or segfault. But after all, this is free software.

A fully working mouse is essential to play this game; problems with the tracker ball would make some of the simpler levels trying, and render the more difficult levels unplayable.

In short, this game is highly addictive and extremely playable. Not recommended for those suffering from RSI - this could exacerbate your problems, and you will probably get frustrated losing on the levels that need fine dexterity. Verdict: worth booting up a Linux distro just to play - though I gather a Mac version and Windows binaries are available.

E*nig"ma (?), n.; pl. Enigmas (#). [L. aenigma, Gr. , fr. to speak darkly, fr. tale, fable.]

1.

A dark, obscure, or inexplicable saying; a riddle; a statement, the hidden meaning of which is to be discovered or guessed.

A custom was among the ancients of proposing an enigma at festivals. Pope.

2.

An action, mode of action, or thing, which cannot be satisfactorily explained; a puzzle; as, his conduct is an enigma.

 

© Webster 1913.

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