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  • 1. CRYPTOGRAPHY SANDHIYA S RANJTHA B
  • 2. CRYPTOGRAPHIC TERMINOLOGY • PLAIN TEXT: The format of the data before encrypted. • CIPHER TEXT: The scrambled format of data after being encrypted. • ENCRYPTION: Method of transforming plain text into an unreadable format. • DECRYPTION: Method of obtaining the encrypted text into plain text.
  • 3. What is Cryptography The art of protecting information by transforming it (Encrypting it) into an unreadable format, called Cipher text, only those who posses a secret key can Decipher or (Decrypt) the message into Plain text.
  • 4. WHY WE NEED A CRYPTOGRAGHY • For confidentiality • For authentication • For data integrity
  • 5. SYMMETRIC KEY ENCRYPTION
  • 6. TYPES OF SYMMETRIC ENCRYPTION oSUBSTITUTION CIPHER oTRANSPOSTION CIPER
  • 7. A- 0 B- 1 C- 2 D- 3 E- 4 F- 5 G- 6 H- 7 I- 8 J- 9 K- 10 L- 11 M-12 N- 13 O- 14 P- 15 Q- 16 R- 17 S- 18 T- 19 U- 20 V- 21 W-22 X- 23 Y- 24 Z- 25
  • 8. PUBLIC /PRIVATE KEY • A public key known to everyone • private or secret key known only to the recipient of the message • When John wants to send a secure message to Jane, he uses Jane's public key to encrypt the message. Jane then uses her private key to decrypt it.
  • 9. ASYMMETRIC KEY ENCRYPTION
  • 10. TYPES OF ASYMMETRIC ALGORITHMS DIFFIE-HELLMAN RSA EI GAMAL ELLIPTIC CURVE CRYPTOGRAPHY(ECC)
  • 11. DIFFIE-HELLMAN METHOD Alice and Bob were communicating each other via mail Eve trying to hack the message To avoid hacking they are using DIFFIE-HELLMAN METHOD
  • 12. EXAMPLE FOR DIFFIE-HELLMAN METHOD alice Bob Eve
  • 13. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve
  • 14. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve
  • 15. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve
  • 16. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve
  • 17. Alice Bob Eve EXAMPLE FOR DIFFIE-HELLMAN METHOD
  • 18. EXAMPLE FOR DIFFIE-HELLMAN METHOD Eve
  • 19. Alice Bob Eve EXAMPLE FOR DIFFIE-HELLMAN METHOD
  • 20. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve 3xmod 17 3xmod 17 3xmod 17
  • 21. EXAPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve 3xmod 17 3xmod 17 3xmod 17 Random Number=15 Random Number=13
  • 22. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve 3xmod 17 3xmod 17 3xmod 17 Random Number=15 Random Number=13 315 mod 17=6 313mod 17=12
  • 23. Alice Bob Eve 3xmod 17 3xmod 17 3xmod 17 Random Number=15 Random Number=13 315 mod 17=6 12 = 313mod 17 6 6 12 12 EXAMPLE FOR DIFFIE-HELLMAN METHOD
  • 24. Alice Bob Eve 3xmod 17 3xmod 17 3xmod 17 Random Number=15 Random Number=13 315 mod 17=6 12 = 313mod 17 6 6 12 12 1215mod 17=10 613mod17=10 EXAMPLE FOR DIFFIE-HELLMAN METHOD
  • 25. Alice Bob Eve 3xmod 17 3xmod 17 3xmod 17 Random Number=15 Random Number=13 315 mod 17=6 12 = 313mod 17 6 6 12 12 1215mod 17=10 613mod17=10 36mod17=15 312mod17=4 EXAMPLE FOR DIFFIE-HELLMAN METHOD