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Introduction to Cryptography

Introduction to Cryptography. Lecture 1. History of Cryptography. Some examples of “ very old” ciphers Modified Hieroglyphics c. 1900 b.c. Atbash, c. 500 b.c. Spartan Scytale, c. 500 b.c. Caesar Cipher, c. 50 b.c. Idea Behind. Is sending the message secure?. Spy. message. Alice. Bob.

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Introduction to Cryptography

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  1. Introduction to Cryptography Lecture 1

  2. History of Cryptography Some examples of “ very old” ciphers • Modified Hieroglyphics c. 1900 b.c. • Atbash, c. 500 b.c. • Spartan Scytale, c. 500 b.c. • Caesar Cipher, c. 50 b.c

  3. Idea Behind • Is sending the message secure? Spy message Alice Bob

  4. Idea Behind • Alice wants to send message to Bob • They share a cipher • Alice encrypt the message • Bob decrypt/decipher the message

  5. Atbash Kh I T Ch Z V H D G B A א ב ג ד ה ו ז ח ט י כ ת ש ר ק צ פ ע ס נ מ ל L M N S O P Tz Q R Sh TH • Use the Atbash cipher to שלומ – Shalom • Shalom mean “Hi” in Hebrow

  6. Spartan Scytale • Wrap a thin strip of parchment helically about a cylindrical rod • Write the message line by line • Remove the rod and send it

  7. Alberti’s Cipher Disk • The inner wheel can be turn • Agree on a letter, for example – b • Agree on number, for example - 6 • Start by giving the corresponding letter - e • Encrypt message • Change cipher after 6 letters

  8. Alberti’s Cipher Disk Example: Agree on letter b, number 8. Message: Secret message YpbzobqjbZqqyec Turn the wheel one step to the right

  9. Homework • Read Section 1.1. • Exercises: 2, 4, 8(Use the wheel in the book) on pg.32-34. • Those questions will be a part of your collected homework.

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