Classical Encryption Techniques

Cryptography and Network Security - Classical Encryption Techniques

1. CS8792 – Cryptography and Network Security ~ S. Janani , AP/CSE KCET Classical Encryption Techniques

2. Contents Basic Terminology Symmetric Encryption model Classical Encryption Techniques Substitution Cipher Transposition Cipher Steganography Rotar Machines

3. Basic Terminology Plaintext – The original message Ciphertext – Coded message Enciphering/Encryption – Process of converting from PT to CT Deciphering/Decryption – Process of converting from CT to PT Cryptography – Study of encryption Cryptanalysis – Techniques used to decrypt a message without any knowledge of encrypting details Cryptology – Cryptography + Cryptanalysis

4. Symmetric Encryption Model Conventional or single key encryption system Was the only type of encryption in prior to public key encryption in 1970’s

5. Model of Symmetric Crypto system

6. 3 Dimensions of Cryptographic System

7. Types of Attacks

8. Bruteforce attack

9. Substitution Techniques Letters of plain texts are replaced by the other letters or by numbers or symbols

10. 1. Caesar Cipher

11. 2. Monoalphabetic cipher

12. 3. Polyalphabetic cipher Uses number of substitutions at different positions of a message

13. Playfair Cipher

14. Hill Cipher Developed by the Mathematician Lester Hill in1929 Strength is that it completely hides single-letter frequencies The use of a larger matrix hides mode frequency information A 3X3 Hill cipher hides not only single-letter but also two-letter frequency information Strong against a ciphertext -only attack but easily broken with a know plaintext attack

15. Vigenere Cipher

16. Vernam Cipher

17. Transposition Cipher

18. Row Columnar Transposition