The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography

by Simon Singh

First came Johannes Trithemius, a German abbot born in 1462, then Giovanni Porta, an Italian scientist born in 1535, and finally Blaise de Vigenère, a French diplomat born in 1523. Vigenère became acquainted with the writings of Alberti, Trithemius and Porta when, at the age of twenty-six, he was sent to Rome on a two-year diplomatic mission.

Vigenère was born in 1523, Porta in 1535. Therefore Porta is 12 years younger than Vigenère. When Vigenère was 26, Porta was 14. So, Vigenère became acquainted with Porta's writings when Porta was 14?

He was also interested in politics and social issues, and toward the end of his life he began a campaign to get rid of the organ grinders and street musicians who roamed London. He complained that the music “not infrequently gives rise to a dance by little ragged urchins, and sometimes half-intoxicated men, who occasionally accompany the noise with their own discordant voices. Another class who are great supporters of street music consists of ladies of elastic virtue and cosmopolitan tendencies, to whom it affords a decent excuse for displaying their fascinations at their open windows.” Unfortunately for Babbage, the musicians fought back by gathering in large groups around his house and playing as loud as possible.

“Propose to an Englishman any principle, or any instrument, however admirable, and you will observe that the whole effort of the English mind is directed to find a difficulty, a defect, or an impossibility in it. If you speak to him of a machine for peeling a potato, he will pronounce it impossible: if you peel a potato with it before his eyes, he will declare it useless, because it will not slice a pineapple.”

In the aftermath of two mass shootings ((today's date is 26-May-2022), this reminds me of the arguments of gun rights advocates: there is no point in doing anything, because nothing we can do will entirely 100% solve every problem in the USA.

Had the telegram never been intercepted or never been published, inevitably the Germans would have done something else that would have brought us in eventually. But the time was already late and, had we delayed much longer, the Allies might have been forced to negotiate. To that extent the Zimmermann telegram altered the course of history … In itself the Zimmermann telegram was only a pebble on the long road of history. But a pebble can kill a Goliath, and this one killed the American illusion that we could go about our business happily separate from other nations. In world affairs it was a German Minister’s minor plot. In the lives of the American people it was the end of innocence.

onetime pad cipher

First mention pf onetime pads at 33% of the book.

An alternative strategy for cracking the Naval Enigma depended on stealing keys. One of the most intrepid plans for stealing keys was concocted by Ian Fleming, creator of James Bond and a member of Naval Intelligence during the war. He suggested crashing a captured German bomber in the English Channel, close to a German ship. The German sailors would then approach the plane to rescue their comrades, whereupon the aircrew, British pilots pretending to be German, would board the ship and capture its codebooks.

After the war, Bletchley’s accomplishments remained a closely guarded secret. Having successfully deciphered messages during the war, Britain wanted to continue its intelligence operations, and was reluctant to divulge its capabilities. In fact, Britain had captured thousands of Enigma machines, and distributed them among its former colonies, who believed that the cipher was as secure as it had seemed to the Germans. The British did nothing to disabuse them of this belief, and routinely deciphered their secret communications in the years that followed.

the English prodigy and polymath Thomas Young. Born in 1773 in Milverton, Somerset, Young was able to read fluently at the age of two. By the age of fourteen he had studied Greek, Latin, French, Italian, Hebrew, Chaldean, Syriac, Samaritan, Arabic, Persian, Turkish and Ethiopic, and when he became a student at Emmanuel College, Cambridge, his brilliance gained him the sobriquet “Phenomenon Young.”

His interest in optics led him toward physics, and another series of discoveries. He published “The Undulatory Theory of Light,” a classic paper on the nature of light; he created a new and better explanation of tides; he formally defined the concept of energy and he published groundbreaking papers on the subject of elasticity.

Meanwhile, in France a promising young linguist, Jean-François Champollion, was prepared to take Young’s ideas to their natural conclusion. Although he was still only in his late twenties, Champollion had been fascinated by hieroglyphics for the best part of two decades. The obsession began in 1800, when the French mathematician Jean-Baptiste Fourier, who had been one of Napoleon’s original Pekinese dogs, introduced the ten-year-old Champollion to his collection of Egyptian antiquities, many of them decorated with bizarre inscriptions.

It is this quality, the power of seeing order in apparent confusion, that has marked the work of all great men.

However, two of Bletchley’s codebreakers, John Tiltman and Bill Tutte, discovered a weakness in the way that the Lorenz cipher was used, a flaw that Bletchley could exploit and thereby read Hitler’s messages.

The NSA employs more mathematicians, buys more computer hardware, and intercepts more messages than any other organization in the world.

Whitfield Diffie is one of the most ebullient cryptographers of his generation. The mere sight of him creates a striking and somewhat contradictory image. His impeccable suit reflects the fact that for most of the 1990s he has been employed by one of America’s giant computer companies-currently his official job title is Distinguished Engineer at Sun Microsystems.

Already by the time this book was published, Sun Microsystems no longer existed, having fallen on hard times and having been bought out by Oracle.

Since Hellman did not have a great deal of funding, he could not afford to employ his new soulmate as a researcher. Instead, Diffie was enrolled as a graduate student.

Ralph, like us, was willing to be a fool. And the way to get to the top of the heap in terms of developing original research is to be a fool, because only fools keep trying. You have idea number 1, you get excited, and it flops. Then you have idea number 2, you get excited, and it flops. Then you have idea number 99, you get excited, and it flops. Only a fool would be excited by the 100th idea, but it might take 100 ideas before one really pays off. Unless you’re foolish enough to be continually excited, you won’t have the motivation, you won’t have the energy to carry it through. God rewards fools.

Now picture the following scenario. As before, Alice wants to send an intensely personal message to Bob. Again, she puts her secret message in an iron box, padlocks it and sends it to Bob. When the box arrives, Bob adds his own padlock and sends the box back to Alice. When Alice receives the box, it is now secured by two padlocks. She removes her own padlock, leaving just Bob’s padlock to secure the box. Finally she sends the box back to Bob. And here is the crucial difference: Bob can now open the box because it is secured only with his own padlock, to which he alone has the key.

Taking the analogy further, imagine that Alice designs a padlock and key. She guards the key, but she manufactures thousands of replica padlocks and distributes them to post offices all over the world. If Bob wants to send a message, he puts it in a box, goes to the local post office, asks for an “Alice padlock” and padlocks the box. Now he is unable to unlock the box, but when Alice receives it she can open it with her unique key.

RSA was first announced in August 1977, when Martin Gardner wrote an article entitled “A New Kind of Cipher that Would Take Millions of Years to Break” for his “Mathematical Games” column in Scientific American.

According to the British Government, public key cryptography was originally invented at the Government Communications Headquarters (GCHQ) in Cheltenham, the top-secret establishment that was formed from the remnants of Bletchley Park after the Second World War. This is a story of remarkable ingenuity, anonymous heroes and a government cover-up that endured for decades.

By the end of 1969, Ellis appears to have reached the same impasse that the Stanford trio would reach in 1975. He had proved to himself that public key cryptography (or nonsecret encryption, as he called it) was possible, and he had developed the concept of separate public keys and private keys. He also knew that he needed to find a special one-way function, one that could be reversed if the receiver had access to a piece of special information. Unfortunately, Ellis was not a mathematician. He experimented with a few mathematical functions, but he soon realized that he would be unable to progress any further on his own.

Cocks was beginning to formulate what would later be known as the RSA asymmetric cipher. Rivest, Shamir and Adleman discovered their formula for public key cryptography in 1977, but four years earlier the young Cambridge graduate was going through exactly the same thought processes. Cocks recalls: “From start to finish, it took me no more than half an hour. I was quite pleased with myself. I thought, ‘Ooh, that’s nice. I’ve been given a problem, and I’ve solved it.’ ”

By 1975, James Ellis, Clifford Cocks and Malcolm Williamson had discovered all the fundamental aspects of public key cryptography, yet they all had to remain silent.

By the early 1980s America’s National Security Agency knew about the work of Ellis, Cocks and Williamson, and it is probably via the NSA that Whitfield Diffie heard a rumor about the British discoveries. In September 1982, Diffie decided to see if there was any truth in the rumor, and he traveled with his wife to Cheltenham in order to talk to James Ellis face-to-face. They met at a local pub, and very quickly Mary was struck by Ellis’s remarkable character:

Already, tens of millions of e-mails are sent each day, and electronic mail will soon become more popular than conventional mail.

Another sign of how dated this book is.

Possibly the greatest allies of the civil libertarian cause are the big corporations. Internet commerce is still in its infancy,

"Internet commerce is still in its infancy" Ha! Not any more.

All of this is done automatically by Alice’s Web browser (e.g., Netscape or Explorer) in conjunction with the company’s computer.

Before going any further, please heed a warning originally given by Niels Bohr, one of the fathers of quantum mechanics: “Anyone who can contemplate quantum mechanics without getting dizzy hasn’t understood it.”

Bohr said that roughly a hundred years ago. A lot of water has passed under the bridge since then. Quantum mechanics is no longer the dizzying mystery it once was.

Indeed, if a message protected by quantum cryptography were ever to be deciphered, it would mean that quantum theory is flawed, which would have devastating implications for physicists; they would be forced to reconsider their understanding of how the universe operates at the most fundamental level.

This is one of the best reason for pursing quantum computing. It might break physics, which is the thing physicists want most in the world.

The Cipher Challenge is a set of ten encrypted messages, which I placed at the end of The Code Book when it was first published in 1999.

Traveling back in time, thanks also go to all the people and institutions that have shaped my career, including Wellington School, Imperial College and the High Energy Physics Group at Cambridge University; Dana Purvis, at the BBC, who gave me my first break in television; and Roger Highfield, at the Daily Telegraph, who encouraged me to write my first article.