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Security - Network Security 1 What do We Need...

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1 Network Security
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Communication Networks © Kang Xi, Polytechnic Institute of NYU 2 What do We Need? Confidentiality You are downloading your credit card statement, if Mr. Hacker captures your packets…. Integrity How to detect a message has been modified… Availability Available to authorized parties Authenticity You have a link to your bank, how do you know it is not Mr. Phisher’s bank?
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Encryption Make the content of a message unreadable to anyone except those possessing special knowledge Special knowledge often consists of a secret key and decryption method Communication Networks © Kang Xi, Polytechnic Institute of NYU 3
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Communication Networks © Kang Xi, Polytechnic Institute of NYU 4 Symmetric Encryption Sender and receiver Share the same Secret Key Sender Encryption algorithm( Plaintext, Key ) Ciphertext Receiver Decryption algorithm( Ciphertext, Key ) Plaintext
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Communication Networks © Kang Xi, Polytechnic Institute of NYU 5 Example Algorithm: XOR Plaintext: 1101 1001 1111 Key: 1001 Cyphertext: 0100 0000 0110 How to attack for the key?
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Communication Networks © Kang Xi, Polytechnic Institute of NYU 6 Cryptanalysis Know both plaintext and cyphertext Exploit algorithm characteristics for keys Example: Plaintext: 1101 1001 1111 Cyphertext: 0100 0000 0110 XOR: 1001 1001 1001
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Communication Networks © Kang Xi, Polytechnic Institute of NYU 7 Brute-force Try all possible keys on cyphertext to get an intelligible plaintext
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Communication Networks © Kang Xi, Polytechnic Institute of NYU 8 Requirements for Strong Encryption Long keys Strong encryption algorithms Computationally infeasible to get the key even if a number of plaintext and the corresponding cyphertext are obtained
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