So, if you shifted the alphabet three places then A=D, B=E, C=F and so on. It works by using the standard alphabet but shifting the letter it begins on by a set number of characters. įor example, one of the simplest forms of substitution is called the Caesar shift cipher, so named because it was favored by Julius Caesar himself. Since this process forms an alphabet that replaces the conventional one, it is referred to as a monoalphabetic cipher. For instance, A=V, B=X and so on until every letter of the alphabet has a substitute pair, thereby forming a cipher alphabet. The other method, substitution, is a system wherein one letter stands for another. For instance, the rail fence cipher, a popular form of transposition, alternates the letters of a message in a zigzag pattern that moves between two consecutive rows. Transposition works by rearranging the letters of a word or sentence to produce a cipher, a secret method of writing.
The result was cryptography, a field that simultaneously developed two distinct branches: transposition and substitution. While secret codes might seem like a relatively modern phenomenon, the earliest known form of cryptography, that is, the practice of concealing the meaning of a message, actually dates back to the fifth century BC! It was at this time that Greece, faced with the constant threat of being conquered by Persia, realized that secure communication was essential.
These book summary will lead you through some of these fateful events, right up to the twentieth century, when codebreakers changed the course of World War II. It was instrumental in historical ruses and schemes, and the very strength of a code had the power to change the course of history it could determine which of two conflicting nations would triumph in a war, or whether someone would live, die, become king or spend the rest of his life in prison. When you were a kid, did you ever invent your own code to exchange top-secret messages with your best friends? There’s something profoundly fascinating about secretive messaging, and humans have been at it for many centuries.Ĭryptography has usually been used by the mighty, but also by those seeking power themselves.
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