Lecture-10-Block-Crpto-2-17-10

Lecture-10-Block-Crp - Modern Cryptographic Techniques DES Modes of Operation RatanGuha CIS3360 SecurityinComputing Spring2010 21710 Lecture10 1

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Modern Cryptographic Techniques DES Modes of Operation Ratan Guha CIS 3360  Security in Computing Spring 2010 2-17-10 Lecture 10 1
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2 Resources Used Cryptography and Network Security, Fourth Edition, by  William Stallings Lecture slides for the textbook by Lawrie Brown Lecture slides by Henric Johnson,Blekinge Institute of  Technology, Sweden
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3 Outline Outline Reading Assignment: Chapter 2 Modern Symmetric Encryption DES Modes of Operation
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Modern Block Ciphers now look at modern block ciphers one of the most widely used types of cryptographic  algorithms  provide secrecy /authentication services focus on DES (Data Encryption Standard) to illustrate block cipher design principles
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Claude Shannon and Substitution-Permutation  Ciphers Claude Shannon introduced idea of substitution-permutation (S-P)  networks in 1949 paper form basis of modern block ciphers  S-P nets are based on the two primitive cryptographic operations  seen before:  substitution (S-box) permutation (P-box) provide confusion & diffusion of message & key
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Confusion and Diffusion cipher needs to completely obscure statistical properties of  original message a one-time pad does this elements to obtain: diffusion  – dissipates statistical structure of plaintext  over bulk of ciphertext confusion  – makes relationship between ciphertext  and key as complex as possible
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Feistel Cipher Structure Horst Feistel devised the  feistel cipher based on concept of invertible product cipher partitions input block into two halves process through multiple rounds which perform a substitution on left data half then have permutation swapping halves implements Shannon’s S-P net concept
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Feistel Cipher Structure
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Feistel Cipher Encryption & Decryption
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Data Encryption Standard (DES) most widely used block cipher in world  adopted in 1977 by NBS (now NIST) as FIPS PUB 46 encrypts 64-bit data using 56-bit key has widespread use has been considerable controversy over its security
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DES Encryption Overview
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This note was uploaded on 10/05/2010 for the course CIS CIS 3360 taught by Professor Guha during the Spring '10 term at University of Central Florida.

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Lecture-10-Block-Crp - Modern Cryptographic Techniques DES Modes of Operation RatanGuha CIS3360 SecurityinComputing Spring2010 21710 Lecture10 1

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