Shannon and 5 Criteria of a good cipher Sina Manavi Manavi.firstname.lastname@example.org 03.11.2011
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“.
Terminology Plaintext: text to be protected Cipher (or cypher): algorithm for performing encryption or decryption Ciphertext: encrypted/decrypted plaintext.
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
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. Undermining security Complexity implementation
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
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
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
Be secureWorld is not safe, be careful of your information and privacy