A modified version of the CFB mode is described below. Consider the plain text is broken into 32-bit fragments M-(M1, M2, M, ], where each M. has 32 bits, rather than the 8 bits used in CFB. Encryption proceeds as follows: an initial 64-bit X, is chosen. Then for i = 1,2,3, , the following is performed: Xi+1 R32(X)11C. = where L32(X) denotes the 32 leftmost bits of X, RsX) denotes the rightmost 32 bits of X, and Xl| Y denotes the string obtained by writing X followed by Y (a) Find the decryption algorithm b) The ciphertext consists of 32-bit blocks C, C> C^ C. Suppose that a transmission error causes C, to be received as C'C, but that C2,C3, C4, are received correctly. This corrupted ciphertext is then decrypted to yield plaintext blocks P,,P: Show that P,"f P, but that P- P, for all i> 3. Therefore, the error affects only three blocks of the decryption. A modified version of the CFB mode is described below. Consider the plain text is broken into 32-bit fragments M-(M1, M2, M, ], where each M. has 32 bits, rather than the 8 bits used in CFB. Encryption proceeds as follows: an initial 64-bit X, is chosen. Then for i = 1,2,3, , the following is performed: Xi+1 R32(X)11C. = where L32(X) denotes the 32 leftmost bits of X, RsX) denotes the rightmost 32 bits of X, and Xl| Y denotes the string obtained by writing X followed by Y (a) Find the decryption algorithm b) The ciphertext consists of 32-bit blocks C, C> C^ C. Suppose that a transmission error causes C, to be received as C'C, but that C2,C3, C4, are received correctly. This corrupted ciphertext is then decrypted to yield plaintext blocks P,,P: Show that P,"f P, but that P- P, for all i> 3. Therefore, the error affects only three blocks of the decryption