# Cryptography & Encryption Secret Codes & The Advance of Technology Copyright © 2008 by Helene G. Kershner.

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Cryptography & Encryption Secret Codes & The Advance of Technology Copyright © 2008 by Helene G. Kershner

Cryptography & Encryption Since the dawn of written language people have used codes. Secret CODE: “a system used for brevity or secrecy of communication, in which arbitrarily chosen words, letters, or symbols are assigned definite meanings.” http://dictionary.reference.com/ http://dictionary.reference.com/ “Codes and ciphers are forms of secret communication. A code replaces words, phrases, or sentences with groups of letters or numbers A cipher rearranges letters or uses substitutes to disguise the message.” http://www.42explore2.com/codes.html http://www.42explore2.com/codes.html A cipher is an algorithm for performing coding (encryption) and decoding (decryption) character. http://en.wikipedia.org/wiki/Encryption http://en.wikipedia.org/wiki/Encryption Copyright © 2008 by Helene G. Kershner

Cryptography & Encryption Who uses secret codes? Governments, military, businesses Doctors, computer uses, almost everyone Why bother? To keep information private To protect information To protect ourselves or to initiate action "One if by land; two if by sea" in “Paul Rever’s Ride” in Longfellow’s poem. http://en.wikipedia.org/wiki/Code_(cryptography) http://en.wikipedia.org/wiki/Code_(cryptography) The BBC broadcast “personal” messages such as: “The princess wears red shoes” & “Mimi's cat is asleep under the table” to direct actions by the French resistance during WW II. http://en.wikipedia.org/wiki/Code_(cryptography) Copyright © 2008 by Helene G. Kershner

Cryptography & Encryption Long and mysterious history Codes used by ancient Hebrews, Babylonians, Egyptions, Greeks and Arabs. Caesar cipher – a code developed by Julius Caesar that substituted each letter of the Roman alphabet for a letter 3- positions down the list. President Jefferson and Lewis & Clark communicated in code when planning for their expedition. The Morse Code is a set of dots and dashes that represents words. Used heavily in both World Wars British built one of the first computers called Colossus to defeat the German coding system called Enigma. Navajo “code talkers” served with the Marines in the Pacific http://en.wikipedia.org/wiki/Encryption Copyright © 2008 by Helene G. Kershner

Cryptography & Encryption How might they work? The Apple is Red 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 the Caesar cipher substitute for letters 3-down the alphabet THE APPLE is Red = WKH DSSOH …. http://en.wikipedia.org/wiki/Encryption Copyright © 2008 by Helene G. Kershner

Cryptography & Encryption Taken on new importance in the Computer Age “Encryption is the process of obscuring information to make it unreadable without special knowledge. To be sure a message is secret we need to know that : the communication is secure the communication is secure it is received by the right “people” it is received by the right “people” it can be decrypted (or decipher) it can be decrypted (or decipher) In other words, we must verify the integrity and authenticity of a message. In other words, we must verify the integrity and authenticity of a message. http://en.wikipedia.org/wiki/Encryption Copyright © 2008 by Helene G. Kershner

Cryptography & Encryption The Government’s Need to Know Vs The Right to Privacy Are these two ideas necessarily at odds? Which should have higher priority? Copyright © 2008 by Helene G. Kershner

Cryptography & Encryption In the mid-1970s, strong encryption went from government agencies to the public domain. WHY? Copyright © 2008 by Helene G. Kershner