Cryptography Assignment on Ciphers with Operation Modes 1. Let E be a block cipher of block length 4 and suppose that Ek(b1b2b3b4) = (b2b3b4b1). Encrypt m - 1011 0001 0100 and decrypt the ciphertext with the following operation modes: (a) ECB mode, (b) CBC mode with IV - 1010, (c) CTR mode with ctr = 1010. 2. Compare ECB, CBC and CTR modes with respect to message expansion, error propagation, pre-computations and parallelization of encryption and decryption. 3. Do the following when encryption works on letters Suppose we have a shift cipher, in which we restrict the possible letter to A-P. Key k-2. Suppose A-P is represented as 0000-1111 as follows A B D E F G H 0000 0001 0010 0011 0100 0101 0110 0111 1 K L M N o P 1000 1001 1010 1011 1100 1101 1110 1111 Given the plaintext=HELLO, calculate the ciphertext with the following operations. 1. ECB mode 2. CBC mode with IV = 0010 3. Counter mode with 11-0001 4. OFB mode with IV = 0010 5. CFB mode with IV = 0010 Cryptography Assignment on Ciphers with Operation Modes 1. Let E be a block cipher of block length 4 and suppose that Ek(b1b2b3b4) = (b2b3b4b1). Encrypt m - 1011 0001 0100 and decrypt the ciphertext with the following operation modes: (a) ECB mode, (b) CBC mode with IV - 1010, (c) CTR mode with ctr = 1010. 2. Compare ECB, CBC and CTR modes with respect to message expansion, error propagation, pre-computations and parallelization of encryption and decryption. 3. Do the following when encryption works on letters Suppose we have a shift cipher, in which we restrict the possible letter to A-P. Key k-2. Suppose A-P is represented as 0000-1111 as follows A B D E F G H 0000 0001 0010 0011 0100 0101 0110 0111 1 K L M N o P 1000 1001 1010 1011 1100 1101 1110 1111 Given the plaintext=HELLO, calculate the ciphertext with the following operations. 1. ECB mode 2. CBC mode with IV = 0010 3. Counter mode with 11-0001 4. OFB mode with IV = 0010 5. CFB mode with IV = 0010