Lecture2 - EasternMediterraneanUniversity...

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LECTURE - II Eastern Mediterranean University School of Computing and  Technology ITEC 443 Cryptography and Network Security
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Roadmap of Cryptography Classical  cryptography (--- 1920s) secret writing required only pen and paper Mostly: transposition, substitution ciphers Easily broken by statistics analysis (e.g., frequency) Mechanical devices invented for encryption Rotor machines (e.g. Enigma cipher)  1930s-1950s featured in films, such as in the James Bond adventure  From  Russia with Love Specification of DES and the invention of RSA (1970s)  --- modern ciphers. Public key system, most notably Quantum Cryptography (future?) 2 Dr. E. Iscioglu                                                    Cryptography and Network  Security
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Example Ex.1: Ciphertext  emag Guess what is plaintext? Plaintext :  game Ex. 2: Ciphertext:   VMBEWZS AMKCZQBG Plaintext:      NETWORK SECURITY If You know the key everything is simple. ..  (ROT+8) 3 Dr. E. Iscioglu                                                    Cryptography and Network  Security
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Overview on the Field of Cryptography CRYPTOLOGY Cryptography Cryptanalysis Symmetric  Key Public  Key Protocols Block  Cipher Stream  Cipher 4 Dr. E. Iscioglu                                                    Cryptography and Network  Security
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History Ancient ciphers Have a history of at least 4000 years  Ancient Egyptians enciphered some of their  hieroglyphic writing on monuments  Ancient Hebrews enciphered certain words in  the scriptures  2000 years ago Julius Caesar used a simple  substitution cipher, now known as the Caesar  cipher  Roger bacon described several methods in  1200s 5 Dr. E. Iscioglu                                                    Cryptography and Network  Security
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History. .. Ancient ciphers Geoffrey Chaucer included several ciphers in  his works  Leon Alberti devised a cipher wheel, and  described the principles of frequency analysis  in the 1460s  Blaise de Vigenère published a book on  polyalphabetic substitution cipher  centuries  6 Dr. E. Iscioglu                                                    Cryptography and Network  Security
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Classical Encryption  Techniques 1. Substitution Techniques a. Caesar Cipher b. Polybius Square c. Playfair Cipher d. Vigenère Cipher e. One-Time Pad 2. Transposition Techniques
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Lecture2 - EasternMediterraneanUniversity...

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