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Encryption Techniques for Secure Internet Communication

Learn about encryption and decryption methods, including Caesar’s cipher and modular arithmetic, to keep your online data safe and secure. Understand how Vigenere Cipher adds an extra layer of protection with unique keyword encryption.

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Encryption Techniques for Secure Internet Communication

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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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