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1-Page Summary of The Code Book
Overview
When you were a kid, did you ever create your own secret code to exchange messages with your friends? Humans have been fascinated by cryptic communication for thousands of years. Cryptography has been used in many historical ruses and schemes. It was instrumental in determining the outcome of wars and whether someone would live or die.
This article will talk about how cryptography and code breaking have evolved over the years. It begins with ancient times, when people used codes to send messages. We’ll learn about how those codes were broken by spies and other people who wanted access to them. The article also talks about technological advances in cryptography and code breaking.
In this article, you will learn how to encrypt your private letters so that only the intended recipient can read them. You will also find out how a weak code had an impact on Mary, Queen of Scots and why your government wants to keep you from using the next state-of-the art encryption method.
Big Idea #1: Secret codes developed early on in human history and evolved quickly.
While cryptography might seem like a modern phenomenon, it actually dates back to the fifth century BC. At that time, Greece was threatened by Persia and realized that secure communication was essential.
The result was cryptography, a field that developed two distinct branches: transposition and substitution.
Transposition involves rearranging letters in a word or sentence to make them unreadable. For instance, the rail fence cipher is one of many examples of transposition and alternates the letters of a message in a zigzag pattern that moves between two consecutive rows.
The other method is called a substitution cipher. In this system, one letter stands for another, such as A=V and B=X. Every letter of the alphabet has a substitute pair until every letter is replaced by its corresponding symbol, forming a new alphabet that replaces the conventional one. This process is known as a monoalphabetic cipher because only one substitution rule was used to create it.
For example, one of the simplest forms of substitution is called the Caesar shift cipher. It works by using the standard alphabet but shifting each letter forward a certain number of places in the alphabet. For instance, if you shifted it three places then A=D, B=E, C=F and so on.
However, simple Caesar shift ciphers were not secure for long. Eventually, people figured out that the keyword cipher was more effective because it added a twist to the monoalphabetic cipher by starting with a keyword or phrase and then continuing with conventional letters but without using those in the keyphrase.
For example, if the keyword was “Caesar,” then the alphabet would begin C, A, E, S… Therefore A=C and B=A.
