11. Security

11. Security - 1 Network Security Communication Networks...

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Unformatted text preview: 1 Network Security 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. Phishers bank? 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 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 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? 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 Communication Networks Kang Xi, Polytechnic Institute of NYU 7 Brute-force Try all possible keys on cyphertext to get an intelligible plaintext Communication Networks Kang Xi, Polytechnic Institute of NYU 8 Requirements for Strong Encryption...
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11. Security - 1 Network Security Communication Networks...

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