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Shannon and 5 Criteria of a good cipher Sina Manavi Manavi.sina@gmail.com 03.11.2011
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Claude Elwood Shannon Shannon Biography (April 30, 1916 – February 24, 2001) American mathematician, electronic engineer, and cryptographer. Graduated from MIT known as "the father of information theory“.
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Terminology Plaintext: text to be protected Cipher (or cypher): algorithm for performing encryption or decryption Ciphertext: encrypted/decrypted plaintext.
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5 criteria of a good cipher:1. The amount of secrecy needed should determine theamount of labor appropriate for the encryption anddecryption. Need of more security, needs more encryption
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5 criteria of a good cipher: 2. The set of keys and the enciphering algorithm should be free from complexity.
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5 criteria of a good cipher: 3. The implementation of the process should be as simple as possible. Undermining security Complexity implementation
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5 criteria of a good cipher: 4. Errors in ciphering should not propagate and cause corruption of further information in the message. one error should not throw off the entire process
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5 criteria of a good cipher: 5. The size of the enciphered text should be no larger than the text of the original message. Longer ciphertext :Easier detection of pattern More space of storage Longer time to communicateby Cryptanalysis
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BUTShannon developed these criteria before modern digitalcomputers.Some the concern he expressed, is not a limitation anymore.We don’t need to implement a simple cipher with modern fastcomputers, whereas complexity of implementation has becomeeasier
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Be secureWorld is not safe, be careful of your information and privacy
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