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Securityand encryption

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  • 1. Security and Encryption
  • 2. What is Encryption?• Information is often stored and transmitted in a file• A plaintext file uses a common encoding format such as ASCII or Unicode to represent the characters of the file.• Encryption is a translation of a file into a format that hides the content from selected parties; a secret code; ciphertext.
  • 3. Uses of Encryption• Privacy/Secrecy • Confidentiality• – email messages • – personnel records• – wireless phones • – medical records• Security• – passwords • – transaction• – wireless networks records• Intellectual • Authentication Property • – digital signatures• – copy protection • – login
  • 4. What Is Cryptography?• Cryptography -- from the Greek for “secret writing” -- is the mathematical “scrambling” of data so that only someone with the necessary key can “unscramble” it.• Cryptography allows secure transmission of private information over insecure channels (for example packet-switched networks).• Cryptography also allows secure storage of sensitive data on any computer.
  • 5. Technology and Risk• Technological advances created new risks ▫ electronic communication makes information more easily available to more parties ▫ long-term storage of sensitive data requires stronger encryption techniques• Some technologies actually reduce risk ▫ fiber optic cable ▫ strong encryption
  • 6. German Enigma Cipher Machine•In 1918, Arthur Scherbius filed for apatent for Enigma Cipher Machineand offered it to the German Navy.• In 1926, German navy begins usingEnigma Machine, lightly modifiedfrom a commercial model.•In 1930, German armed forcesintroduced asignificantly modified military model.
  • 7. Simple Cryptography
  • 8. Two basic principles• Substitution• THIS IS A SECRET (key n=3)• WKLV LV D VHFUHW• Transposition• THIS IS A SECRET (key 4213)• IHSTSI S EAERTC
  • 9. Caesar Cipher
  • 10. Rotating Key Cipher
  • 11. Goals of Cipher:• Diffussion: ▫ 􀂉 Small change in plaintext, changes lots of ciphertext ▫ 􀂉 Statistical properties of plaintext hidden in ciphertext• 􀂉 Confusion: ▫ 􀂉 Statistical relationship between key and ciphertext as complex as possible ▫ 􀂉 So, need to design functions that produce output that is diffuse and confused
  • 12. General Principles• Longer keys make better ciphers• 􀂉 Random keys make better ciphers• 􀂉 Good ciphers produce “random” ciphertext• 􀂉 Best keys are used once and thrown away
  • 13. Public Key Cryptography• Your turn….. ▫ What is it? ▫ How does it work? ▫ Include an analogy ▫ Any weaknesses? ▫ If you come across digital signatures, what are they? ▫ Use MS Word