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The History of Codebreaking, Part I: The Pre-Computing Era (Preview Edition) Jason Hale Cipher – Early Techniques

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The History of Codebreaking, Part I: The Pre-Computing Era(Preview Edition)

Jason Hale

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Cipher – Early Techniques

Long been recognized by governments as an important tool in support of diplomacy and military action, and have set up organizations devoted to intercepting and decrypting messages of other powers.

- Pen and paper techniques

- Language knowledge and statistical techniques

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Early Adopters of Cryptography

Julius Caesar – 1st Century B.C.

Al-Kindi: 9th Century Muslim Arab Scientist, was responsible for the first known recorded explanation of cryptoanalysis (Wikipedia)

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Conventional Cryptograhy

Simple Substitution Cipher

Caesar’s Cipher



Using this scheme, the plaintext,

"SECRET" encrypts as "VHFUHW."

To allow someone else to read the ciphertext, you tell them that the key is 3.

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Since 1988, the most commonly chosen letters (R,S,T,L,N,E) are given to the contestant automatically.


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Frequency Analysis

Caesar's Cipher is so vulnerable to frequency analysis.

One-to-one relationship between each letter.

If a sufficiently large ciphertext is given, the plaintext can be found out by frequency analysis


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Frequency Analysis

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Frequency Analysis: Digraphs

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The Zimmerman Telegram – WW I

  • 1917 U.S. : NO code-breaking ability.- Germany to Mexico, in Code 7500 and 13042

  • Intercepted in Britain and decoded by British Naval Intelligence

“We intend to begin on the first of February unrestricted submarine warfare. We shall endeavor in spite of this to keep the United States of America neutral”

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1930’s Europe

Germany: Secretly Rearming

USSR: Threatening

France, Poland, Britain, others:Spying to see what Germany would do.

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Significance of Breaking Enigma

  • Responsible for the Outcomes of Some Individual Battles:

  • the decimation of the Italian Fleet at Matapan in March 1941

  • the sinking of the Scharnhorst in December 1943

  • helped Britain to defeat the U-boats in the Atlantic between October and November 1941 (evasive routing). (untold merchant ships were saved from sinking, even as number of Uboats increased in 41-42.

  • Contributed to the outright defeat of U-Boats in the Atlantic in 43-44.

  • Overlord would probably have had to been delayed 2 years without defeating the U-Boats

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Defining characteristics of five first operative digital computers

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After the War computers

  • British Secrecy:

    • 1945 Collusus machines ordered destroyed by Winston Churchill

    • Existence Classified until 1970

  • American companies continued building and improving computers for commercial and especially military use.

  • ENIAC – Artillery Tables; H-BOMB (1946 – 1955) Aberdeen Proving Grounds- EDVAC - $500,000 binary computer (1951-1960) US. Ballistics LaboratoryUS National Security Agency (NSA) – Established 1952

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NSA has the world's largest supercomputing facility. computersSome of the earliest supercomputers were designed and built for the National Security Agency.

The Cray XMP-22 was the first Cray supercomputer ever delivered to a customer site – NSA.

NSA is believed to be the U.S.’ largest employer of mathematicians.

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Snow White by the Brothers Grimm. Retold by Jennifer Greenway. Illus. by Erin Augenstine. Kansas City, MS: Ariel Books, 1991.

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How ENIGMA Worked computers

if a German wanted to send a message saying 'Hitler ist in Wilhelmshaven',

the Enigma operator would tap the H key on his keyboard and

write down on his notepad which bulb on the Enigma's lightboard lit up.

Hitting a key on the Enigma keyboard released an electric current which ran to a series of scrambling elements – including a plugboard and three wheels. The scrambling elements diverted the current away from its original course. The current would then hit a 'reflector' end disk which would send the current back through the same scrambling elements again, though on a different course, and the current would finish up by lighting a bulb marked with one of the letters of the alphabet

The way the plugboard and the wheels were set determined what cipher text was produced. The plugboard looked like a telephone switchboard. The settings lists which Schmidt passed to the French Secret Service specified how all Enigma operators and receivers during a particular quarter should set the plugs connecting the plugboard sockets.

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How ENIGMA Worked computers

The wheel order to be used by all Enigma operators, which might be, say,

wheel 1 on the right, wheel 3 in the middle, and wheel 2 on the left, was,

like the plugboard socket connections, specified in the settings lists

provided by Schmidt. The wheel on the right turned anti-clockwise one

twenty-sixth of a revolution each time a keyboard key was pressed.

This meant that if an Enigma operator pressed the H key on the keyboard

twice consecutively, the current would go into the right wheel's right face

at a different point on each occasion, it would follow a different pathway

through the wheels, and it would usually light up a different letter

Another element regulated by these settings lists was the ring,

marked with the twenty-six letters of the alphabet, which was around the rim

of each wheel. The ring could be rotated relative to the inner core of the wheel,

and then fixed into position with a catch. The settings at which the rings were

fixed were referred to as the Ringstellung by the Germans. If the ring setting

on a wheel was, say, A, the ring had to be rotated manually until the A on the

ring was opposite the Ringstellung marker, which was a red dot on the catch

on some Enigma machines. The letters around the ring – visible through a

window above the wheel once the wheel was in its working position inside

the Enigma machine – were used by message senders to describe the position

of the wheel to message receivers.

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How ENIGMA Worked computers

The rings also had another function. A notch on each ring ensured that the wheel placed on its left turned one twenty-sixth of a revolution whenever the ring reached a particular position in its cycle. This position was different for each of the three wheels. So, for example, when wheel 1 was placed on the right, the ring on wheel 1 ensured that the middle wheel turned one twenty-sixth of a revolution anti-clockwise if Q was showing through the window above the right wheel when a keyboard key was tapped. The middle wheel was turned as the right wheel turned so that R rather than Q was showing through the window above the right wheel. (The 'turnover positions' for wheels 2 and 3 were at E and V respectively.) The middle wheel would then remain in the position to which it had turned until the keyboard keys were tapped twenty-five more times, by which time the right wheel would have rotated one complete revolution. At this point Q would once again be showing through the window above the right wheel, and the ring around the right wheel would then ensure that the middle wheel turned another. one twenty-sixth of a revolution when the next keyboard key was tapped. Following the same principle, the left wheel would be turned one twenty-sixth of a revolution each time the middle wheel passed its 'turnover position'. After the three wheels were set to a particular position, they would only return to their original position after the keyboard keys had been tapped about 17,000 times

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Das Boot computersThe Eye of the Needle

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First Guy computersRadio Guy – broke several simpler German ciphers – Antoni PalluthThree Mathematician he introduced to Cipher Breaking, moved to Warsaw,

To work on ciphers part-time.Rózycki* and Zygalski Marian Rejewski was the first that was asked to work on ENIGMA, and given the manuals.

These manuals(photos of) which were smuggled out of Germany by France’s ENIGMA spy made it clear that an Enigma was used to scramble

the letters making up the words in a message before it was sent out

in morse code by a radio transmitter

if a German wanted to send a message saying 'Hitler ist in Wilhelmshaven',

the Enigma operator would tap the H key on his keyboard and

write down on his notepad which bulb on the Enigma's lightboard lit up. Schmidt's manuals also explained how an Enigma machine produced the cipher text

The Polish Cipher Bureau

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The Polish Cipher Bureau computers

Rejewski knew that if he was to break the code, he would first have to construct a replica Enigma machine. To do this he worked out a formula which, he hoped, would enable him to discover the wiring inside the wheel which was placed on the right . He believed the settings from Schmidt (in August 32) for Sept-Oct 32 would help him do so.He made some GUESSES, and one of them proved correct, from which he, was able to work out the wiring in the wheels Mathematically, with the help from an example setting and message from the manual.Once he knew how the enigma’s were wired, his team was able to build some replicas.

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The American Role in Breaking Enigma computers

Hollywood film U-571 – Gave Americans TOO MUCH credit for capturing ENIGMA technology

were able (after May 2003) to produce and manufacture machines

which could break the Enigma regularly even after the

Germans added the fourth wheel to their cipher machines

The British engineers had been unable to design

equivalent machinery which was reliable.

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Hans Thilo Schmidt computers

German Defence Ministry Cipher Office executive who in 1931 gave the French Secret Service their first clues (for profit) on how to break the

Enigma code (2 years before NAZIs assumed power)

Was betrayed by his French Spy Master to the Germans and arrested by the Gestapo in March 1943

Poisoned himself with cyanide procured by his daughter

Untended, unmarked grave outside of Berlin

Average, middle-class guy. Wife and 2 small kids.Economic problems when Germany’s economy tanked. Had affairs with a string of uglier maids and others. Charlotte and Martha, insulting gifts. Loved a lot of women.Inability to resist temptation. (Would never be able to work for the NSA now.)Had access to the safe where cipher machines were stored.Contacted French Secret Service. Sold them manuals that described how theCipher machines worked. (And documents with their current settings?)Initially 10,000 marks for 2 manuals (2001 equivalent of 2,000 francs)

According to the French crypotographers: manuals explained how to encipher

a message, but they did not enable a cryptographer to read Enigma messages.2nd opinion from British.


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They agreed with their French counterparts that Schmidt's computersdocuments would not enable them to crack the Enigma.

He also provided setting instructions, and information about Germanrearmament, the latter mailed in letters written in invisible ink.

Sometimes he would sneak over into Belgium, for meetings with theFrench, to deliver photographs of settings documents, etc. As he made more and more money, he and is wife took an a lavish lifestyle—expensive suits, and expensive ski vacations in Switzerland, and other European vacations, which the French were concerned would attract attention in Germany. He continued going to bars in Berlin, as well, as though he were notmarried. When they encourage him to settle down, he enlarged his house andbuilt a small factory producing fat for soap producers. This was a front, to looklike this was where is money was coming from.

Speaking French to each other, then denying they knew French when theirchildren needed help with their homework.

In 1936, informed the French, 2 months in advance, of Germany’s plans invade the Rhineland, thanks to information from his brother, Rodolf Schmidt, anArmy General.


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The ENIGMA Spy computers

quickly, he should telephone Georges Blun, a French journalist based in Berlin.

If Schmidt slipped into the conversation the words 'Uncle Kurt has died',

Blun would know that Schmidt needed to see him immediately.

Both men would then go to the waiting room in the Charlottenburg railway station in Berlin He passed along the information with a map that showed the nations and timelines that Germany planned to invade: Austria in Fall 38; Check. In Spring 39; Poland in Fall 39. However, when the French spymastertelegrammed this information back to France, some of it, the Germans intercepted and decoded the telegram, and so they knew that they hada leak. Schmidt knew they knew, and the French knew they knew,and so they set up new cautions, such as a new address in Geneva to send his letters to, and a new kind of invisible ink.

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U-33 – German U-Boat computers

was sunk on 12 February 1940 while attempting to lay mines in the

Firth of Clyde, one of Britain's busiest estuaries, off the west coast of Scotland 25 members of the crew buried in a German military cemetery at Cannock Chase

in Staffordshire, Germany.

groups of identical grey granite rectangular gravestones

Every year on 12 February, the anniversary of their death,

flowers are laid beside their gravestones

Max Schiller, a twenty-sixth member of the crew, survived. He was 18. One of the older officers had pleaded with him to sit next to him, because the older

Officer thought he was going to die.One of the survivors (which one?) failed to discard two Enigma wheels in his pocket,which were retrieved by the British when he was rescued.

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U-559 – German U-Boat computers

Was crippled and abandoned in the Eastern Medeterianian, 30 Oct 42

one of the most courageous and significant acts of the Second World War.

The HMS Pertard was conducting a search for a German U-Boat

U-559 had surfaced and was being abandoned by its crewLt. Francis Anthony Blair Fasson and Able Seaman Colin Grazier swam to the UBoat and recovered some ENIGMA code books before the U-BOATsank with them in it

Codebreakers needed the books, in addition to their brains (why? Wouldcomputers have made a difference?)

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Enigma - Weaknesses computers

- German U-boat commanders didn’t’ destroy books and devices before trying to scuttle their boats.- German Naval Command Didn’t test to see if Enigma had been compromised, once there was evidence that it might have been. (What evidence?)- Each wheel in the Enigma had a different “turnover position” – it turned over the wheel placed next to it in a different position in the former wheel’s cycle. (DEMO?) All Turing had to do to crack the cipher, “once some of the codebooks were caputred, was to identify the position at which the wheels in the machine were turning over the wheels next to them.” NEED TO UNDERSTAND BETTER.


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Significance of Breaking Other Ciphers computers

- U.S. broke the Japanese military code and learned of plans to invade Midway Island.

- Believed to have shortened the War in the Pacific by at least one year.

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Enigma computers

Some wheels—not all devices had the same wheels? How did it operate?How many wheels? (4th after 1 Feb ’42) – blinded Bletchley Park for 10 and ½ months.

First used in 1930 – three years prior to Nazi takeover.

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U-Boats in WWII computers


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German Blind Eye computers

Paradoxically, the greatest threat to the Allies winning the war at sea was the danger that they would sink too many ships too quickly, thereby alerting the German Naval Command to the possibility that this was because its ciphers were being read.


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Bomba computers

Bomba ("Polish for Bomb"): a special-purpose machien designed in October 1938 by Poland's Rejewski to break the German Enigman machine ciphers.

There was a new cipher each day, and Bomba could break it in about two hours. They had been breaking the messages for years, but Bomba automated the process. German machine got more sophisticated, but then it started to taking more time.

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National Cryptologic School

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Colossus computers

Colossus - used by the British. an early electronic digital computer. Operational by 1944. Ten had been constructed by the end of the war.

To decipher teleprinter messages which had been encrypted using the Lorenz SZ40/42 machines.

Very secret - information not available until late 1970s

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Alan Turing computers

Alan Turing also worked for the British code-breaking effort, on the Enigma system

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ENIAC computers

1945 or 6: ENIAC - first large scale, digitial, general purpose computer. Designed for calculating artillery firing tables, and was used in the development of the

hydrogen bomb. (cost $500,000)

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NSA computers

1952: National Security Agency established in the United States, for this purpose. It was established by

2002 - 50th anniversary, there was speculation that the days when ciphers, or codes, could be broken by mathematical means were numbered.

Was instrumental in driving the market for high performance computing in the later 20th century--including the first general purpose computers in the US, and the first "supercomputers", the first parallel computer. Often underwriting the effort.

It would take a lot of computing power to break a code, and to dechiper a message, and with the increasing threat of nuclear attack, there was not much time