Cryptography and Network Security final 2024 with 100% correct answers

Distinguish between symmetric-key and asymmetric-key cryptosystems. Answer - Aysmmetric key cryptography utilizes two separate keys, a public and a private key, as opposed to symmetric key cryptography, which only utilizes one key. While encryption and decryption in symmetric key cryptography is based on substitutions and permutations of symbols, encryption in asymmetric key cryptography is based off of applying mathematical functions to numbers. Distinguish between public and private keys in an asymmetric-key cryptosystem. Answer - There are two keys used in asymmetric key cryptography: a public and a private key. The public key corresponds to encryption and the private key is used in decryption. The public key is distributed to the community, while the private key is kept secret and used to decrypt messages encrypted utilizing the public key. Distinguish between a one-way function and a trapdoor one-way function. Answer - A one-way function is any function that satisfies two properties: 1. The function f is simple to compute. 2. The inverse of f is nearly impossible to compute. This means that the function only goes one way, and cannot be undone by finding the inverse of the output. A trapdoor one-way function satisfies a third property: 3. Given the output of f and a trapdoor, or secret, x of f(x) = y can be computed easily. Distinguish between message integrity and message authentication. Answer - Message integrity is the concept that, besides being encrypted, the integrity of each message needs to be preserved. Meaning that messages cannot be manipulated or changed by attackers. Message authentication is the concept that, in addition to sending a message, the receiver should also receive some form of proof that the message is coming from the sender instead of an imposter.