1. Consider a block cipher where the block size is one byte and the encryption (and decryption) algorithm is XORing the plaintext block with a one-byte key. Given a plaintext and a key with the following values: = = Encrypt the plaintext using the following modes of operation: (a) Electronic codebook (ECB) mode. (6 pts) (b) Cipher block chaining (CBC) mode with initial value of = (assume padding is not used). (6 pts) (c) Counter (CTR) mode with a four-bit nonce = and a four-bit counter that starts at zero. (6 pts) 2. Assuming you are using a 64-bit (8-byte) block cipher in CBC mode. Show the results of padding the following plantexts so they can fit into an even number of blocks using the padding scheme discussed in class. (4 pts each) (a) 0f8353c2 8e1ff6 (b) 8c521e (c) c1 (d) 9f6bef2c 902fe4ba 3. Assume a LFSR has a 4-bit state and a feedback function that XORs the first and third bit from the left. Given the following initial states, list out all of the states the LFSR cycles through, the period, and the sequence of output bits that are repeated. All numbers are in binary notation. (4 pts each) (a) 0000 (b) 0001 (c) 0011 (d) 0110