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Internet Encryption Methods Overview

Understand encryption and decryption methods like Caesar’s cipher and Vigenere cipher on the internet. Learn about text key encryption and decryption using modular arithmetic. Explore examples for better understanding of cybersecurity concepts.

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Internet Encryption Methods Overview

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  1. Encryption on the Internet EirikAlbrigtsen

  2. Encryption & Decryption Text Unreadable Text key + encryption method Unreadable Text Text key + decryption method

  3. Caesar’scipher

  4. Modular Arithmetic 18 = 6 mod 12 15 = 3 mod 12 26 = 2 mod 12, as 26 and 2 are 2*12 apart General mathematical statement: a = b mod N  a and b are a multiple of N apart

  5. Caesar’s cipher A=0, B=1, C=2, ... , Y=24, Z=25. To encrypt x: E(x) = x+3 mod 26 • Example: • C = 2, E(2) = 2+3 mod 26 = 5 = F • Y=24, E(24) = 24+3 mod 26 = 27 mod 26 = 1 = B

  6. Caesar’s cipher the quick brown fox jumps over the lazy dog WKH TXLFN EURZQ IRA MXPSV RYHU WKH ODCB GRJ

  7. Security of Caesar’s cipher To decrypt x: D(x) = x-3 mod 26 K=3=shift factor Max 25 possible values of K.

  8. Security of Caesar’s cipher

  9. Vigenere Cipher • Keyword K = ADHD = 0373 (length 4) • Encrypt separately each letter depending on its position in the message. If the position is of the form:0+4n: shift by 01+4n: shift by 32+4n: shift by 73+4n: shift by 3 • Example • X = BOB BOB = 11411141 • E(X) = BRI EOB = 11784144

  10. security = secrecy security = published and attacked, but not broken.

  11. Trust This

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