EngE_1104_Summer_2006_Lab_12_Students_Copy_V1A_TW -...

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Explorations Of Our Digital Future Summer 2006 Lab 12 – Cryptography Lab Copyright by: Jeremy Garrett and Tom Walker, July 6, 2006 Lab Objective: To learn about the history of cryptography (code making) and about the encryption method used by computers, the internet, and other digital devices. Lab Description: In the previous lab we explored the ways in which computers detect binary errors and how they compress data. In this lab we will start by exploring some simple, yet very important ways of building codes, specifically “rotation” and “substitution.” Then we will study Blaise de Vigenère’s Le chiffre indéchiffrable (which is French for “the unbreakable code”). Then we will finish by exploring the ways in which variations on these old techniques make our credit cards and other computer data secure in a world full of professional “hackers.” Part 1 – Substitution Codes: Part 1 – Background: In our modern world we often think of codes / encryption techniques as mysterious, mathematical processes that only sophisticated computers can use. While it is true that the strongest codes (such as the one used for credit card information during online purchases), do involve the use of large numbers and multi-step mathematical procedures, all of the encryption methods are actually fairly simple. More importantly though, these “modern” digital methods of encoding a message are simply digital variations of techniques that have been used since people first started keeping secrets from each other. One of the most straight forward methods of making a code is to simply replace each letter or each word with a different one. The most famous example from this century comes from the brave Native Americans who volunteered for the dangerous job of “code talker” during the two world wars. The Navajo tribesmen who served the marines during WWII were so successful that Major Howard Connor, 5th Marine Division signal officer, declared, “Were it not for the Navajos, the Marines would never have taken Iwo Jima.” Because of that success and the potential need for their future assistance, the US military refused, until recently, to release information about these brave men and the major contributions that they made. Fortunately though, the US government did honor these men in 1992 with a special memorial. Additionally, the US government has been hard at work to add more men and more tribes to the honored list as more information has become available. http://www.history.navy.mil/faqs/faq61-2.htm
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Part 1 – Report: 1. As a quick warm-up exercise, encrypt the sentence “I love Math,” using the simple substitution code shown below, and record your results. 2.
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This note was uploaded on 09/19/2011 for the course ENGE 1114 taught by Professor Twknott during the Fall '06 term at Virginia Tech.

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EngE_1104_Summer_2006_Lab_12_Students_Copy_V1A_TW -...

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