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# Cryptography.

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### Cryptography.

1. 1. CRYPTOGRAPHY SANDHIYA S RANJTHA B
2. 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. 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. 4. WHY WE NEED A CRYPTOGRAGHY • For confidentiality • For authentication • For data integrity
5. 5. SYMMETRIC KEY ENCRYPTION
6. 6. TYPES OF SYMMETRIC ENCRYPTION oSUBSTITUTION CIPHER oTRANSPOSTION CIPER
7. 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. 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. 9. ASYMMETRIC KEY ENCRYPTION
10. 10. TYPES OF ASYMMETRIC ALGORITHMS DIFFIE-HELLMAN RSA EI GAMAL ELLIPTIC CURVE CRYPTOGRAPHY(ECC)
11. 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. 12. EXAMPLE FOR DIFFIE-HELLMAN METHOD alice Bob Eve
13. 13. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve
14. 14. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve
15. 15. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve
16. 16. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve
17. 17. Alice Bob Eve EXAMPLE FOR DIFFIE-HELLMAN METHOD
18. 18. EXAMPLE FOR DIFFIE-HELLMAN METHOD Eve
19. 19. Alice Bob Eve EXAMPLE FOR DIFFIE-HELLMAN METHOD
20. 20. EXAMPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve 3xmod 17 3xmod 17 3xmod 17
21. 21. EXAPLE FOR DIFFIE-HELLMAN METHOD Alice Bob Eve 3xmod 17 3xmod 17 3xmod 17 Random Number=15 Random Number=13
22. 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. 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. 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. 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