Encryption: A Brief History Author: Margery Waldron

Encryption l Encryption is the process of converting messages and documents into a secret code to ensure privacy. l Encryption has fascinated people of all ages throughout history l Encryption is used today in many fields including the internet, banking and CIA.

Cryptography l Cryptography is the field of computer science that studies encryption and decryption, which is the process of “breaking the code”. l Code: a “code” uses substitute words, numbers or symbols in place of each word in the secret message. l Cipher: a “cipher” uses numbers or symbols for every letter in the secret message

Polybius Polybius: A Greek historian captured during Roman conquest of Greece in 168 BC who made a cipher to send secret messages Polybius’ secret code was called the Polybius’ Square Key

Polybius’ Square Key To write a message using this code, simply write the two numbers that intersect at the letter you want. For example 51 = U. Using this cipher, figure out the message below: ’ ! A B C D E F G H I J K L M N O P Q R S T U V W X Y/Z

Caesar's Shift Caesar’s Shift Cipher: Roman Emperor Julius Caesar invented this cipher which gives a number to each letter of the alphabet by shifting the alphabet three places to the right: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Using Caesar’s cipher, decode this: ?

Alan Turing Alan Turing: an English math scholar who worked as a code breaker for the Government Code and Cypher School during WWII. He is responsible for breaking the German’s “Enigma code” used to communicate with their submarines which helped turn the war around for the allies. He went on to design one of the first computers called the “turing machine” in He was also an Olympic long distance runner!

Prime numbers & Cryptography Cryptographers use prime numbers to encrypt code because when they are large, they are very hard to locate. In 1977, a group of cryptographers challenged other cryptographers to find the key to their brand-new code. The only way to do it was to find the prime factors of a certain number that was 129 digits long!! At that time, the cryptographers figured it would take about 40 quadrillion (40 x ) years for others to solve the puzzle and crack the code. This problem was solved in the spring in 1994 in a time span of just 8 months by 160 computers working together via the Internet on a solution!!

Beale's Buried Treasure During the 19th century, a young man named Thomas Jefferson Beale appeared in Lynchburg, Virginia. After two years, he left an iron box with a trusted friend before leaving again. Beale told the friend that the box was not to be opened until 10 years had passed without his return. The decade passed with no sign of Beale. The box was opened and inside it were papers that described a spectacular buried treasure and directions on where to find it. However, the directions were nothing but three pages of numbers! (These numbers are printed in their entirety in Paul Hoffman’s book, Archimedes’ Revenge if you want to have a look!) The owner of the box was unable to decipher the code and when he died 41 years later, he left it with another man named James Ward.

Beale's Buried Treasure Years later, Ward was able to decipher one of the pages because he discovered that Thomas Jefferson Beale had used for a cipher key: the Declaration of Independence! By numbering each word of the Declaration of Independence, Ward hit upon the solution and was able to decipher the entire page. However, that page told only that the treasure consisted of thousands of pounds of gold and silver and millions of dollars’ worth of jewels, not where it was buried. Cryptographers have been trying for over 170 years, without success, to decipher the other pages or find the treasure. Even today, using modern computers, the cipher remains a mystery.

Beale's Buried Treasure Declaration of Independence When in the course of human events it becomes necessary for

Ms. Waldron's Secret Message l You are going to be given a file called secretcode.dat that contains a secret message. l You will create a class called Cypher that contains your substitution Cipher. l You will write a java application that uses the Cypher class to decrypt the secret message.

Mrs. Waldron's Buried Treasure The secret message is written using a substitution cipher. That is every letter in the Alphabet has been changed to a different letter. You need to substitute letters of the alphabet with what you guess is the corresponding encoded letter. You can reassign the letter if you change your mind.

Ms. Waldron’s Secret Message The templates for the Cypher Class and Decrypt.java are on our web site. Now we will have a demonstration…