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Network Security

Network Security. Section 1: Introduction to security. What is Security?. SIMPLE BUT HARD TO DO !. What is the biggest enemy for humans ? H U M A N S ! We need security until the people with bad minds exists! What is the best solution for security ? No high-tech hardware

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Network Security

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  1. Network Security Section 1: Introduction to security

  2. What is Security? SIMPLE BUT HARD TO DO! • What is the biggest enemy for humans? H U M A N S! • We need security until the people with bad minds exists! • What is the best solution for security? No high-tech hardware No high-tech software Change the way of thinking!

  3. Why security? • Why Linux is more secure than Windows? Popularity of Windows • Why Firefox is more secure that IE? Popularity of IE • Why network security is not important in IRAN? Unpopularity of information in computers

  4. What is Network Security? Confidentiality C I A Integrity Availability

  5. People with bad minds

  6. Network Security Problems • Secrecy • Authentication • Non-repudiation • Integrity Control

  7. Physical vs. Network Security • Security in real word • Voice, Face, Handwritting • Security in Network • Cryptography, Digital Signature

  8. Cryptography • Cryptography Lexicon • Cipher vs. Code • Plaintext, Key, Cipher text • Crypto analysis • Cryptology • Work Factor

  9. C = Ek(P) & P = Dk(C) • C: Cipher text, K: Key, P: Plaintext • E: Encryption Function • D: Decryption Function • Dk(Ek(P)) = ? • Main Rule for Cryptography: Algorithm must be clear for all only key is hidden. • Security by obscurity

  10. Crack Cipher text • Problems: • Cipher text Only • Known Plaintext • Chosen Plaintext • Cipher text only • Do you think it’s not crack able? Yes! No, What is your idea?

  11. Substitution Cipher • One or group of character(s) substitute with another character. • A => D, B => E, C => F. • Attack => DWWDFN • kths character substitution. • What is your idea for cracking it? • Estimating usual character, Estimating usual word

  12. Transposition Cipher • Change the situation/ Transpose of characters. Any idea for cracking this kind of encryption?

  13. One-Time Pads What are the problems? Long pads Hard to transportation • Use random key. • Not crack able at all! Because of information theory. • Example: I LOVE YOU!

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