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

by Simon Singh

Furthermore, the archaeological codebreaker often has no idea of the context or contents of an ancient text, clues which military codebreakers can normally rely on to help them crack a cipher.

That is to say, in most cases of archaeological decipherment there was no deliberate attempt by the original scribe to hide the meaning of the text.

The earliest hieroglyphics date back to 3000 B.C., and this form of ornate writing endured for the next three and a half thousand years. Although

Hence, evolving in parallel with hieroglyphics was hieratic, an everyday script in which each hieroglyphic symbol was replaced by a stylized representation which was quicker and easier to write. In about 600 B.C., hieratic was replaced by an even simpler script known as demotic, the name being derived from the Greek demotika meaning “popular,” which reflects its secular function.

All three forms of writing are phonetic, which is to say that the characters largely represent distinct sounds, just like the letters in the English alphabet.

The spread of the Christian Church was responsible for the extinction of the Egyptian scripts, outlawing their use in order to eradicate any link with Egypt’s pagan past. The ancient scripts were replaced with Coptic, a script consisting of 24 letters from the Greek alphabet supplemented by six demotic characters used for Egyptian sounds not expressed in Greek.

The ancient Egyptian language continued to be spoken, and evolved into what became known as the Coptic language, but in due course both the Coptic language and script were displaced by the spread of Arabic in the eleventh century.

The belief that hieroglyphics is merely picture writing was even commonly held by foreigners who visited Egypt while hieroglyphics was still a living script.

Young seemed to be able to tackle problems in almost any subject, but this was not entirely to his advantage. His mind was so easily fascinated that he would leap from subject to subject, embarking on a new problem before polishing off the last one.

Scribes tended to write in such a way as to avoid gaps and maintain visual harmony; sometimes they would even swap letters around in direct contradiction to any sensible phonetic spelling, merely to increase the beauty of an inscription.

Fourier explained that nobody could interpret this cryptic writing, whereupon the boy promised that one day he would solve the mystery.

The great difficulty in deciphering the remaining scripts is that there are no cribs, nothing which allows the codebreaker to prize open the meanings of these ancient texts.

Linear B, a Cretan script dating back to the Bronze Age, was deciphered without any helpful clues bequeathed by ancient scribes.

However, it appeared that the palace at Knossos had been destroyed by fire, baking the tablets and helping to preserve them for three thousand years.

First, the direction of the writing was clearly from left to right, as any gap at the end of a line was generally on the right.

Purely alphabetic scripts tend to have between 20 and 40 characters (Russian, for example, has 36 signs, and Arabic has 28). At the other extreme, scripts that rely on semagrams tend to have hundreds or even thousands of signs (Chinese has over 5,000). Syllabic scripts occupy the middle ground, with between 50 and 100 syllabic characters.

When A.J.B. Wace, Professor of Archaeology at the University of Cambridge, spoke in favor of the theory that Linear B represented Greek, Sir Arthur excluded him from all excavations, and forced him to retire from the British School in Athens.

After the death of Sir Arthur Evans the Linear B archive of tablets and his own archaeological notes were available only to a restricted circle of archaeologists, namely those who supported his theory that Linear B represented a distinct Minoan language. However, in the mid-1940s, Alice Kober, a classicist at Brooklyn College, managed to gain access to the material, and began a meticulous and impartial analysis of the script. To those who knew her only in passing, Kober seemed quite ordinary-a dowdy professor, neither charming nor charismatic, with a rather matter-of-fact approach to life. However, her passion for her research was immeasurable.

She concluded that Linear B represented a highly inflective language, meaning that word endings are changed in order to reflect gender, tense, case and so on.

Ventris published his ideas about vowel signs, and his extensions to the grid, in a series of Work Notes, which he sent out to other Linear B researchers.

They could now exploit the speed and flexibility of programmable computers to search through all possible keys until the correct one was found.

The first difference is that a mechanical cipher machine is limited by what can be practically built, whereas a computer can mimic a hypothetical cipher machine of immense complexity.

Electronics can operate far more quickly than mechanical scramblers: a computer programmed to mimic the Enigma cipher could encipher a lengthy message in an instant.

Before encryption, any message must therefore be converted into binary digits. This conversion can be performed according to various protocols, such as the American Standard Code for Information Interchange, known familiarly by the acronym ASCII, pronounced “asskey.”

Even though we are dealing with computers and numbers, and not machines and letters, the encryption still proceeds by the age-old principles of substitution and transposition, in which elements of the message are substituted for other elements, or their positions are switched, or both. Every encipherment, no matter how complex, can be broken down into combinations of these simple operations.

Computer encryption was restricted to those who had computers, which in the early days meant the government and the military.

In 1947, AT&T Bell Laboratories invented the transistor, a cheap alternative to the electronic valve.

In 1953 IBM launched its first computer, and four years later it introduced Fortran, a programming language that allowed “ordinary” people to write computer programs. Then, in 1959, the invention of the integrated circuit heralded a new era of computing.

For some years after, he suppressed his interest in cryptography to avoid arousing the suspicions of the American authorities.

The NSA did not object to Feistel’s past, they merely wanted to have a monopoly on cryptographic research, and it seems that they arranged for Feistel’s research project to be canceled. In the 1960s Feistel moved to the Mitre Corporation, but the NSA continued to apply pressure and forced him to abandon his work for a second time. Feistel eventually ended up at IBM’s Thomas J. Watson Laboratory near New York, where for several years he was able to conduct his research without being harassed.

Lucifer was so strong that it offered the possibility of an encryption standard that was probably beyond the codebreaking capabilities of the NSA; not surprisingly, the NSA did not want to see an encryption standard that they could not break.

The NSA argued in favor of limiting the number of keys to roughly 100,000,000,000,000,000 (technically referred to as 56 bits, because this number consists of 56 digits when written in binary).

The 56-bit version of Feistel’s Lucifer cipher was officially adopted on November 23, 1976, and was called the Data Encryption Standard (DES).

Key distribution might seem a mundane issue, but it became the overriding problem for postwar cryptographers.

Diffie is aware that his dress and personality can have quite an impact on others, and comments that, “People always think that I am taller than I really am, and I’m told it’s the Tigger effect—‘No matter his weight in pounds, shillings and ounces, he always seems bigger because of the bounces.’ ”

As a child he became fascinated by mathematics, reading books ranging from The Chemical Rubber Company Handbook of Mathematical Tables to G.H. Hardy’s Course of Pure Mathematics.

He then took a series of jobs related to computer security, and by the early 1970s he had matured into one of the few truly independent security experts, a freethinking cryptographer, not employed by the government or by any of the big corporations.

Back in the 1960s, the U.S. Department of Defense began funding a cutting-edge research organization called the Advanced Research Projects Agency (ARPA), and one of ARPA’s front-line projects was to find a way of connecting military computers across vast distances.

The main aim was to make the Pentagon’s computer infrastructure more robust in the face of nuclear attack, but the network would also allow scientists to send messages to each other, and perform calculations by exploiting the spare capacity of remote computers.

At the end of the 1980s, non-academic and nongovernmental users were given access to the Internet, and thereafter the number of users exploded.

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.

Order is crucial even with a monoalphabetic substitution cipher.

Furthermore, we can think of all forms of computer encryption as functions because they turn one number (the plaintext) into another number (the ciphertext).

For this reason, one-way functions are sometimes called Humpty Dumpty functions.

Functions performed in the modular arithmetic environment tend to behave erratically, which in turn sometimes makes them one-way functions.

Often, the only way to reverse a function in modular arithmetic is to compile a table by calculating the function for many values of x until the right answer is found.

Diffie, Hellman and Merkle publicly demonstrated their discovery at the National Computer Conference in June 1976, and astonished the audience of cryptoexperts.

He often went through long periods of barren contemplation, and on one occasion in 1975 he became so frustrated that he told Mary that he was just a failed scientist who would never amount to anything. He even told her that she ought to find someone else. Mary told him that she had absolute faith in him, and just two weeks later Diffie came up with his truly brilliant idea.

Anybody can close a padlock simply by clicking it shut, but only the person who has the key can open it.

Nevertheless, by the end of 1976 the team of Diffie, Hellman and Merkle had revolutionized the world of cryptography. They had persuaded the rest of the world that there was a solution to the key distribution problem, and had created Diffie–Hellman–Merkle key exchange—a workable but imperfect system. They had also proposed the concept of an asymmetric cipher—a perfect but as yet unworkable system.