cse443-lecture-5-cryptography

# cse443-lecture-5-cryptography - Lecture 5 - Cryptography...

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CMPSC 443 Introduction to Computer and Network Security - Spring 2012 - Professors Jaeger Lecture 5 - Cryptography CMPSC 443 - Spring 2012 Introduction Computer and Network Security Professor Jaeger www.cse.psu.edu/~tjaeger/cse443-s12/

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CMPSC 443 Introduction to Computer and Network Security - Spring 2012 - Professor Jaeger Page A historical moment . .. The enigma machine was used to secure communication of german military throughout the second world war . .. ... and it changed the course of human history. 2
CMPSC 443 Introduction to Computer and Network Security - Spring 2012 - Professor Jaeger Page Intuition • Cryptography is the art (and sometimes science) of secret writing – Less well know is that it is also used to guarantee other properties, e.g., authenticity of data – This is an enormously deep and important Feld – However, much of our trust in these systems is based on faith (particularly in efFcient secret key algorithms) Cryptographers create ciphers - Cryptography Cryptanalyst break ciphers - Cryptanalysis The history of cryptography is an arms race between cryptographers and cryptanalysts. 3

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CMPSC 443 Introduction to Computer and Network Security - Spring 2012 - Professor Jaeger Page Cryptosystem A cryptosystem is a 5-tuple consisting of Where, E is an encryption algorithm D is an decryption algorithm M is the set of plaintexts K is the set of keys C is the set of ciphertexts 4 ( E , D , M , K , C ) E : M × K C D : C × K M
CMPSC 443 Introduction to Computer and Network Security - Spring 2012 - Professor Jaeger Page What is a key? • A key is an input to a cryptographic algorithm used to obtain confdentiality, integrity, authenticity or other property over some data. – The security oF the cryptosystem oFten depends on keeping the key secret to some set oF parties. – The

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## cse443-lecture-5-cryptography - Lecture 5 - Cryptography...

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