Shannon and 5 good criteria of a good cipher
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Transcript of Shannon and 5 good criteria of a good cipher
(April 30, 1916 – February 24, 2001)
American mathematician, electronic engineer, and cryptographer.
Graduated from MIT known as "the father of
information theory“.
Claude Elwood Shannon Shannon Biography
Plaintext: text to be protected
Cipher (or cypher): algorithm for performing encryption or decryption
Ciphertext: encrypted/decrypted plaintext.
Terminology
1. The amount of secrecy needed should determine the amount of labor appropriate for the encryption and decryption. Need of more security, needs more encryption
5 criteria of a good cipher:
2. The set of keys and the enciphering algorithm should be free from complexity.
5 criteria of a good cipher:
3. The implementation of the process should be as simple as possible.
5 criteria of a good cipher:
Undermining security
Complexity implementati
on
Message Transmission
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
5 criteria of a good cipher:
5. The size of the enciphered text should be no larger than the text of the original message.
5 criteria of a good cipher:
Longer ciphertext :
More space of storageEasier detection of pattern by Cryptanalysis
Longer time to communicate
Shannon developed these criteria before modern digital computers.
Some the concern he expressed, is not a limitation anymore.
We don’t need to implement a simple cipher with modern fast computers, whereas complexity of implementation has become easier
BUT
World is not safe, be careful of your information and privacy
Be secure