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Lecture+26+-+Security - CS170Lecture26 Security...

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CS 170 Lecture 26 Security Kristian Stout [email protected] Office IN: Livingston Student Center, A lounge near “the rock” and the commuter lounge. Office Hours: TTH 5:30 – 6:30
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Types of attacks  (In communication) Interruption Eg cutting a cable.  Interception Eg Wiretapping, packet sniffing Modification Eg file tampering Fabrication Eg spoofing
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Encryption And Decryption Encryption Terminology Encryption : Transforming plaintext to cipher text using a  key/cipher and an encryption algorithm, so that the information  becomes unreadable to unauthorized parties. Cryptosystem : A combination of encryption and  decryption methods Cleartext  or  Plaintext : Information before encryption  Cipher text : Information in encrypted form Decryption : Reversing encryption process. Converting cipher text  to plain text. Encryption algorithm and encryption key are different.
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Symmetric Cryptography: Caesar Encryption Simple substitution system.  Replaces every letter with another letter after  shifting by three. For example:   D  E  F and so on Algorithm: Substitution, Key: Shift by k For more information: Modular Arithmetic
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XOR: An Encryption Operation Exclusive OR: Interesting way to apply a key to  cleartext Combines two bits by rule: If the bits are the 
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