Intro to Cryptography WGU C839 Module 2| 62 QUESTIONS| WITH COMPLETE SOLUTIONS

The same key is used to encrypt messages as well as decrypt messages. These algorithms are always faster but have an issue with exchanging keys. CORRECT ANSWERS: Symmetric Cryptography Modern cryptography began when Claude Shannon publish "Communication Theory of Secrecy Systems" in 1949. He focused on this concept by quantifying information, leading to a number of methods for encrypting and decrypting information. CORRECT ANSWERS: Information Theory Change to one character in plain text affect multiple characters in the cipher text. CORRECT ANSWERS: Diffusion Attempts to make the relationship between statistical frequencies of the cipher text and the actual key as complex as possible. Uses complex substitution algorithms. CORRECT ANSWERS: Confusion A small change yields large effects in the output. Fiestel's variation on Claude Shannon's concept of diffusion. Ideally, a change in one bit of plaintext would change all the bits in the ciphertext. CORRECT ANSWERS: Avalanche A cryptosystem should be secure even if everything about the system, except the key, is publicly known. CORRECT ANSWERS: Kerckhoffs's Principle C = E(k,p) expresses what mathematically? CORRECT ANSWERS: Symmetric Algorithm for Encryption P = D(k,c) expresses what mathematically? CORRECT ANSWERS: Symmetric Algorithm for Decryption Changing some part of the plain text for some matching part of the cipher text is? CORRECT ANSWERS: Substitution Swapping of blocks of cipher text. given a sentence "I like icecream" you could swap every three-letter sequence (or block) with the next and get: "ikel I creiceam" Modern versions do this at the level of bits or blocks of bits. CORRECT ANSWERS: Transposition Asks if there is a ONE in BOTH the first and second number. If both numbers have a ONE in BOTH places the resultant number is ON