Q6: A blockcipher normally can be considered as a pseudorandom permutation, i.e. E:Kx{0,1}123 + {0,1}128, where K is the key space. When encrypting a picture m, say with n = 105 blocks (each with 128 bits, total about 1.5 megabytes), and we use an ECB mode, i.e., C = E(k, mi),..., Gr = E(k, m). It is very common that the picture has many identical blocks, e.g., mi = m2 = ...,= mk, explain why ECB mode will reveal this pattern? and how about other mode, such as counter mode? A counter mode encryption generates ciphertext as c = E(k,1)em, 2 = E(k, 2) m2, ...,C=E(k,n) om, and here 1,2,3,..., n are all treated as a 128-bit binary string, assuming n