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Unformatted text preview: 1 Introduction Reading assignment: Chapter 1 of Katz & Lindell Cryptography MerriamWebster Online Dictionary: 1. secret writing 2. the enciphering and deciphering of messages in secret code or cipher. Scientific study of techniques for securing digital information, transactions, and distributed computations. 2 3 Computational Difficulty (OneWay Functions) Pseudorandom Generators And Functions ZeroKnowledge Proof Systems Encryption Schemes Crypto Protocols Sign/MAC Schemes APPLICATIONS A Structural View of Cryptography 4 Basic objectives of cryptography Protecting data privacy Data integrity (message authentication): allowing the recipient to check if a received message has been modified. Authentication: Data origin authentication: allowing the recipient to verify the origin of a received message. Entity authentication: allowing the entities of a (connection oriented) communication to authenticate each other. Nonrepudiation: to prevent the sender from later denying that he sent the message. 5 Main Characters Alice Bob Peggy (prover) Vic (verifier) Eve or Oscar (eavesdropper, opponent) 6 Bob Alice Eve 7 m c E D Bob Alice m key key’ Encryption and secrecy Plaintext ciphertext plaintext 8 Encryption and secrecy Encryption protects secrecy of transmitted messages Encryption E k : plaintext m → ciphertext c Decryption D k’ : ciphertext c → plaintext m Encryption key: Decryption key: equal or not equal k k ′ 9 Symmetrickey encryption Also called secretkey or privatekey encryption Encryption key = decryption key D(k, E(k,m)) = m Or, D k (E k (m)) = m 10 Example: Caesar’s shift cipher Plaintexts m English characters...
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This note was uploaded on 01/22/2011 for the course CSE 794 taught by Professor Tenh.lai during the Spring '10 term at Ohio State.
 Spring '10
 TenH.Lai

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