1. NUMBER THEORY Chapter 5: Cryptology

2. Era of Electronic Electronic communication Electronic Banking

3. Terminology Cryptology: Discipline Cryptography: Design & Implementation Cryptoanalysis: Breaking the system

4. Terminology Plaintext: secret message Cipher: method to alter the plaintext Cybertext: message has been altered

5. Terminology encryption/enciphering: process decryption/deciphering: process

6. Letter ↔ Integer

7. CAESAR CIPHER Character Cipher

17. Exercise

18. How to decipher?

24. Exercise

25. AFFINE TRANSFORMATION Character Cipher

26. Complete system of residue!

31. Exercise:

33. Secure? Character cipher is not safe

35. frequency

41. VIGENERE CIPHER Block Cipher

42. Ci=Pi+ki

43. Exercise Use the key “SECRET”

44. DIGRAPHIC CIPHER Block Cipher

46. Numerical equivalent

52. VERNAM CIPHER Stream Cipher

54. AUTOKEY VERNAM CIPHER Stream Cipher

56. Exercise Cipher Text Seed – F Plain Text ?

57. EXPONENTIATION CIPHER Cryptology

65. Deciphering

66. Fermat’s theorem

67. p=2633, e=29

68. PUBLIC KEY CRYPTOLOGY Cryptology

69. RSA Ciphering System

73. Deciphering Euclidean Algorithm

75. Factorizing prime? n=pq What is the factor of following number? 1522605027922533360535618378132637429 7180681149613806886579084945801229632 58952897654000350692006139

76. 3797522793694367392280887275544562785 4565536638199 × 4009469095092088103068373529276146838 9214899724061