I'm not sure what I have to do for this question. Suppose E1 and E2 are two encryption methods. Let K1 and K2 be keys and consider the double encryption EK1, K2(m)=EK11(EK22(m)).

1. Suppose you know a plaintextciphertext pair. Show how to perform a meet-in-the-middle attack on this double encryption.

2. An affine encryption given by xx+ (mod 26) can be regarded as a double encryption, where one encryption is multiplying the plaintext by and the other is a shift by . Assume that you have a plaintext and ciphertext that are long enough that and are unique. Show that the meet-in-the-middle attack from part (a) takes at most 38 steps (not including the comparisons between the lists). Note that this is much faster than a brute force search through all 312 keys.