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
- 9. Classical Encryption Techniques Substitution Techniques Caesar Cipher Monoalphabetic Cipher Polyalphabetic Cipher Vigenere Cipher Playfair Cipher Hill Cipher Vernam Cipher Transposition Techniques Railfence Row Column Transposition
- 10. Substitution Techniques • Letters of plain texts are replaced by the other letters or by numbers or symbols
- 11. 1. Caesar Cipher
- 15. 3. Polyalphabetic cipher • Uses number of substitutions at different positions of a message
- 16. Playfair Cipher
- 18. 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
- 20. Vigenere Cipher
- 22. Vernam Cipher