INTRO TO CRYPTOGRAPHY WGU C839 MODULE 5 QUESTIONS AND ANSWERS WITH SOLUTIONS 2025

Finding any method to decrypt the message that is more efficient that simple brute force attempts. - ANSWER Breaking Ciphers Simply trying every possible key to decrypt a message - ANSWER Brute Force Using other techniques to attempt to derive the key, can be used to test the efficacy of a cryptographic algorithm. Frequently used to test hash algorithms for collisions. - ANSWER Cryptanalysis The most basic tool for breaking classic ciphers like the Caesar and Vigenere Ciphers. Analysis the frequency of certain letters of the alphabet to derive some information about the key that was used. - ANSWER Frequency Analysis This method is used for attacking polyalphabetic substitution ciphers, such as the Vigenere Cipher. Used to deduce the length of the keyword used in the polyalphabetic substitution, the longer ciphertext the more effective this method becomes. - ANSWER Kasiski Method or Test The attacker obtains ciphertexts corresponding to the set of plaintexts of his own choosing. This is difficult but not impossible - ANSWER Chosen Plaintext Attack The attacker only has access to a collection of ciphertexts. It is much more likely then a known plaintext attack, but is also the most difficult. This attack is completely successful if the corresponding plaintexts can be deduced, or the key. Obtaining any information about the underlying plaintext is still considered a success. - ANSWER Chosen Ciphertext Only Like a chosen-plaintext attack, except the attacker can obtain ciphertext encrypted under two different keys. Very useful if you can obtain the plaintext and matching ciphertext. - ANSWER Related-key Attack Based on finding affine approximations to the action of the cipher. Most commonly used on block ciphers. Known as a p