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An Introduction to Cryptography

An Introduction to Cryptography. What is cryptography?. noun krip-ˈtä-grə-fē : the process of writing or reading secret messages or codes. “ Encryption ”: to put into a format that is unreadable to unauthorized individuals “ Cipher ”: a method of encryption, or a code. Basics. History.

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An Introduction to Cryptography

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  1. An Introduction to Cryptography

  2. What is cryptography? noun \krip-ˈtä-grə-fē\ : the process of writing or reading secret messages or codes • “Encryption”: to put into a format that is unreadable to unauthorized individuals • “Cipher”: a method of encryption, or a code

  3. Basics

  4. History

  5. History

  6. Substitution Cipher • Substitute one value for another

  7. Substitution Cipher Common example: Cryptograms in newspapers

  8. Substitution Cipher • Original message: “plaintext”: • Encrypted message: “ciphertext”

  9. Solve this Substitution Cipher XKGTJDHI

  10. Solution SECURITY

  11. Ciphers in Popular Culture “National Treasure” (2004)

  12. Keys • They are what we use to secure the messages. (And to decrypt them!) • They are shared to decrypt the message.

  13. Keys • “Asymmetric” cryptography has two keys: • Public key: used to encrypt the message • Private key: used to decrypt the message. (This one is secret) • Mathematically matched to protect the message

  14. Vigenere Square • Polyalphabetic cipher • Column letter: plaintext • Row Letter: key Example:

  15. Vigenere Square Encrypt this word:

  16. Solution VDOZF

  17. Ciphers in Popular Culture “A Beautiful Mind” (2001)

  18. Transposition Cipher Rearranges values within a block to create ciphertext • Example: • “Caesar Block Cipher” • Uses 5X5 square • Message contains <25 characters Famously created by Julius Caesar!

  19. Caesar Block Cipher Plaintext: LEARN ABOUT ENCRYPTION read across fill down Ciphertext: LTROEAYNABEPEONTNUCI

  20. Caesar Block Cipher • Try writing and encrypting your own message! • Remember: <25 characters (including spaces) read across • Pass it to a friend to decrypt fill down

  21. Advanced Cryptography • Using the types of techniques we learned, computers can encrypt files, emails, etc. • Makes communication secure • But we still need to protect our keys and passwords!

  22. Advanced Cryptography Technology Example

  23. Real World Application • Cryptanalysts: study information systems to find hidden aspects • It’s their job to decrypt messages

  24. Why does this matter to you? • When you put your personal information on the internet, make it hard for thieves to steal Check your passwords: http://www.passwordmeter.com/

  25. Create a strong password • Start with a weak password: • Linda!Marie1207 • Come up with a secret key (4-6 characters) • puppy • Encrypt text using the vigenere square: • Accsy!Bugxc1207 • Strong Password

  26. Jeopardy!

  27. Questions

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