Cyber Security Chapter 2, solve question 18

Question 17 2 pts Problem 2.3b - Consider the simple symmetric block encryption algorithm, in which 64 bit blocks of plain text text are encrypted using a 128 bit key denoted by K. The Encryption Algorithm is C (P XOR KO) ADD K1 where C is the cipher text, KO is the leftmost 64 bits of key K, K1 is the rightmost 64 bits of key K, XOR is bit-wise XOR, and ADD is addition mod 2 24 Suppose the adversary has obtained two pairs of plaintext and corresponding cipertext, P1,C1 and P2,C2 The adversary observes that -C2 (P2 XOR KO) ADD-K1 and can compute C1 ADD -C2: C1 ADD -C2 (P1 XOR KO) ADD K1) ADD (P2 XOR KO) ADD-K1) (P1 XOR K0) ADD (P2 XOR KO). In other words, the adversary knows C1 ADD-C2 = (P1 XOR KO) ADD (P2 XOR KO, The adversary knows C1, C2, P1, and P2: Which of the following statements is true? o The adversary cannot solve for KO because XOR and ADD operators are not associative or distributive with one another o Using basic algebra, the adversary can now solve for KO O Knowing KO is not sufficient to learn K1 Question 18 2 pts Problem 2.3a - Consider the simple symmetric block encryption algorithm, in which 64 bit blocks of plain text text are encrypted using a 128 bit key denoted by K. The Encryption Algorithm is where C is the cipher text, KO is the leftmost 64 bits of key K, K1 is the rightmost 64 bits of key K, XOR is 24 bit-wise XOR, and ADD is addition mod 2 The decryption equation is P-[eq] Note you can only use the symbols XOR ADD KO K1 P C-KO-K1 ()