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

by Simon Singh

The monoalphabetic substitution cipher is the general name given to any substitution cipher in which the cipher alphabet consists of either letters or symbols, or a mix of both.

Technically, a code is defined as substitution at the level of words or phrases, whereas a cipher is defined as substitution at the level of letters. Hence the term encipher means to scramble a message using a cipher, while encode means to scramble a message using a code.

A nomenclator is a system of encryption that relies on a cipher alphabet, which is used to encrypt the majority of a message, and a limited list of codewords.

Cryptographers have come to realize that it requires a great deal of time, effort and money to create a random key. The best random keys are created by harnessing natural physical processes, such as radioactivity, which is known to exhibit truly random behavior.

For example, the hotline between the presidents of Russia and America is secured via a onetime pad cipher.

Although the elaborate symbols of hieroglyphics were ideal for the walls of majestic temples (the Greek word hieroglyphica means “sacred carvings”), they were overly complicated for keeping track of mundane transactions. 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.

semagrams—that these intricate characters represented whole ideas, and were nothing more than primitive picture writing.

The Rosetta Stone, as it became known, appeared to be the equivalent of a cryptanalytic crib, just like the cribs that helped the codebreakers at Bletchley Park to break into Enigma.

the four fundamental principles of hieroglyphics. First, the language of the script is at least related to Coptic, and, indeed, examination of other hieroglyphics showed that it was Coptic pure and simple. Second, semagrams are used to represent some words, e.g., the word “sun” is represented by a simple picture of the sun. Third, some long words are built wholly or partly using the rebus principle. Finally, for most of their writing, the ancient scribes relied on using a relatively conventional phonetic alphabet.

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

Certification authorities are organizations that will verify that a public key does indeed correspond to a particular person.

A quantum computer defies common sense. Ignoring the details for a moment, a quantum computer can be thought of in two different ways, depending on which quantum interpretation you prefer. Some physicists view the quantum computer as a single entity that performs the same calculation simultaneously on 128 numbers. Others view it as 128 entities, each in a separate universe, each performing just one calculation.