INFR 2600U Lecture Notes - Lecture 2: Data Encryption Standard, Symmetric-Key Algorithm, Strong Cryptography
28 Sep 2017
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Document Summary
Universal technique for providing confidentiality for transmitted or stored data. Also known as conventional encryption or single-key encryption. Two requirements for secure use: strong encryption algorithm & sender/receiver must have obtained copies of the secret key in a secure fashion and must keep the key secure. Cryptanalytic attacks : rely on : nature of the algorithm, some knowledge of the general characteristics of the plaintext, some samples plaintext-cipher text pairs. Exploits the characteristics of the algorithm to attempt to deduce a specific plaintext or the key being used. If successful, all future and past messages encrypted with that key are compromised. Brute-force attack : try all possible keys on some cipher text until an intelligible translation into plaintext is obtained. On average, half of all possible keys must be tried to achieve success. Fips pub 46: referred to as the data encryption algorithm, uses 64 bit plaintext block and 56 bit key to produce a 64 bit cipher text block.
