ConnectionsHow cracking the Enigma,winning a World War,inventing the iPod/iPhone/iPad,and Alan Turing are related

It starts with a boy fascinated by science…

Alan Turning (b 1911) in India, which was still a British colony at the time.

Conducted experiments and studied latest research with friends

Studied math and logic at Cambridge

…who became the father of computer science

The state of math in 1930s-crisis Gödel’s incompleteness theorem in

mathematics.There are some questions in mathematics

that are beyond the reach of logical proof. These statements cannot be proven true or false with reason and logic. These are called undecidable questions.

Alan Turing tried to solve this problem:“It’s about the difficulty of telling right from wrong.

People think—most people think—that in math we always know what is right and what is wrong. Not so. Not any more.”

What makes a question decidable or not?

Imagine a machine that follows a precise algorithm, or “mechanical recipe” (multiply 2 numbers in a series of steps).

This imaginary machine has parts An infinite tape for storing data (much like a magnetic tape or a

modern hard disk). A read head that reads and writes data. A finite memory for storing some data of the tape. An instruction set for controlling how the read head should read,

write and move.

This imaginary machine is very similar to the modern day computer

The Big Idea of Computer Science

The Church-Turing Thesis: Any calculation that is possible (a decidable

question) can by performed by an algorithm (program) running on a Universal Turing Machine (computer) provided sufficient space and time are available.

All of this work was done 10 years before anything resembling an electronic computer was even invented.

A big question—code breaking Simple Codes-Substitution

Important point: the encoded version of a particular letter is always the same.

Frequency analysis is the key to breaking the code.

A tough code-Enigma

State of the art in Germany in WWII159,000,000,000,000,000,000

possible keysThought to be unbreakable

How it works

1. Set rotors to key for day.2. Press letter (plaintext) (W)3. Observe light (ciphertext) (I)4. Rotors shift automatically,

wiring changes.5. Repeat 2 Key Points

The encoded version of a particular letter changes every time the rotors shift.

Impenetrable to frequency analysis. All ciphertext letters have same frequency.

But Enigma wasn’t perfect Patterns can be found in rotor settings. There is an

algorithm that the enigma uses to encode letters, therefore, you can build a machine to follow an algorithm to decode letters.

Some human problems: German military efficiency leads to sending out encrypted weather reports at 6am every day. “wetter” is the first word of these reports.

Design flaw—a letter will never be encoded as itself. What then is the meaning of a 300 letter

message with no A’s?

Turing cracks Enigma Churchill “ACTION THIS DAY: Make sure Turing has all he

wants on extreme priority and report to me that this has been done.”

Turing designs the Bombe, a machine that can test hundreds of Enigma settings automatically and ultimately crack the encryption scheme.

Impact on the war

Provided clear picture German troop concentrations along French coast on D-Day.

“I do not imagine that any war since classical times, if ever, has been fought in which one side read consistently the main military and naval intelligence of the other.” —British cryptoanalyist

Some intelligence had to go unused to keep the Germans from suspecting their communications had been compromised.

Many feel that Bletchly Park’s achievements in cracking Enigma was the decisive factor in the war.

Shortened the war and saved thousands of lives (on both sides).

…from code-breaking to the birth of the iPod

Remember the Big Idea Any calculation that is possible (a decidable

question) can by performed by an algorithm (program) running on a Universal Turing Machine (computer) provided sufficient space and time are available.

Birth of the iPod Write music down digitally on a hard disk. Build a machine to read and write to disk. Write an algorithm (program) to manipulate the

data on the disk and send it to a speaker. An iPod is just a Turing machine.

But that’s just the beginning A computer is a universal machine.

You can program your iPod to record your voice. You could program your iPod to edit your songs. Every imaginable (possible) operation can be done to your data

(photos and video are just the beginning). Add a phone, data connection and camera, and the options

become as big as your imagination (iPhone). Now what happens when you add a big screen (iPad)?

There’s a good chance that you won’t use any paper-based textbooks in college.

Some negative consequences Every bad use of your data is also possible (file sharing, illegal

copying). Computers can be exploited to do bad things just as easily as

they can be used to do good things.

So What’s the Connection to Today?

Alan Turing wasn’t just One of the greatest mathematicians of

the 20th centuryOne of the key figures in the allied

Victory in WWIIThe father of computer science and

the iPod/iPhone/iPad…

Alan Turing was a homosexual

And he was silenced…

In 1952, He admitted a homosexual relationship to London Police.

He was charged, tried and convicted of “Gross Indecency contrary to Section 11 of the Criminal Law Amendment Act of 1885.”

He was publicly humiliated in the British press.

The British Government withdrew his security clearance, forced him to consult a psychiatrist and undergo hormone treatment.

The Other Side of Alan Turing

He became depressed and committed suicide in on June 7, 1954.

He died at the age of 42, still in the prime of his life.

Where would we be today if Alan Turing had not been

silenced?

Please help end the silence

Had he lived, he would be 97 years old today.

www.dayofsilence.org

Just this past year…Prime Minister Gordon Brown issues apology (Sept 10, 2009):“Thousands of people have come together to demand justice for Alan Turing and

recognition of the appalling way he was treated. While Turing was dealt with under the law of the time and we can’t put the clock back, his treatment was of course utterly unfair and I am pleased to have the chance to say how deeply sorry I and we all are for what happened to him. Alan and the many thousands of other gay men who were convicted as he was convicted under homophobic laws were treated terribly. Over the years millions more lived in fear of conviction.

I am proud that those days are gone and that in the last 12 years this government has done so much to make life fairer and more equal for our LGBT community. This recognition of Alan’s status as one of Britain’s most famous victims of homophobia is another step towards equality and long overdue.

…So on behalf of the British government, and all those who live freely thanks to

Alan’s work I am very proud to say: we’re sorry, you deserved so much better.”

Just a couple of months ago