Security in Information Systems: Chapter 4 - Cryptography & Key Exchange Protocols

Cryptography & Key Exchange Protocols Faculty of Computer Science & Engineering HCMC University of Technology Outline 1 Cryptography-related concepts 2 Key channel for symmetric cryptosystems 3 Perfect encryption 4 Dolev-Yao threat model 5 Protocol “message authentication” 6 Protocol “challenge-response” 7 Public-key cryptosystems Ho Chi Minh City University of Technology Faculty of Computer Science and Engineering © 2011 Information Systems Security Chapter 2: Cryptography & Key Exchange Protocols 2 Cryptography-related concepts  Plaintext is the original content which is readable as textual material. Plaintext needs protecting.  Ciphertext is the result of encryption performed on plaintext using an algorithm. Ciphertext is not readable.  Encryption is the process of turning plaintext into ciphertext, decryption is the inverse of the encryption.  Encryption, decryption process needs keys  Cryptosystems = encryption + decryption algorithms Ho Chi Minh City University of Technology Faculty of Computer Science and Engineering © 2011 Information Systems Security Chapter 2: Cryptography & Key Exchange Protocols 3 Cryptosystems KeyE Plaintext Ciphertext Hello, This content is confidential …................... ……………….. …. Encryption Cryptosystem Decryption À¿¾«§¶   ……………… … ……………… … ….. KeyD Ho Chi Minh City University of Technology Faculty of Computer Science and Engineering © 2011 Information Systems Security Chapter 2: Cryptography & Key Exchange Protocols 4 Cryptography-related concepts  Symmetric (shared-/secret-key) cryptosystem: the same key for (en/de)cryption algorithms  Asymmetric (public-key) cryptosystem: public & private keys for (en/de)cryption algorithms ke = kd ke ≠ kd Ho Chi Minh City University of Technology Faculty of Computer Science and Engineering © 2011 Information Systems Security Chapter 2: Cryptography & Key Exchange Protocols 5 ... - tailieumienphi.vn