LetM1 = {0000 0001, 0101 0000, 1111 1000} be a message space andM2 = {1010 0100, 1110 0011, 1011 0101} be another. (In case the typesetting is unclear, these are sets containing three bitstrings of length 8.) Suppose two ciphertexts are received c1 = 1011 1011 and c2 = 0101 1110. Suppose you know c1 is a one-time pad encryption of a message in M1 with key k and that c2 is one-time pad encryption of a message in M2 with the same key k. What are the two messages and what is the key?

Let IV, c1, c2, c3, . . . be a CBC-mode encryption of message m1, m2, m3, . . . , where each message block mi is n-bits long. Suppose an attacker (who does not know the key) knows the first block m1 (e.g., it is predictable header information). Suppose m01 is a different n-bit string. Show how the attacker can make a new ciphertext IV 0 , c01 , c02 , c03 , . . . which decrypts to m01 , m2, m3, . . . , even though they do not know the key that was used for the encryption.

Alice and Bob want to communicate securely over an insecure channel where Evecould be listening. To ensure their message remains confidential, they decide to usea simple substitution cipher for encryption and decryption, where each letter in thealphabet is shifted by a fixed number of places.For this exercise, use a shift of 3 places to the right (a Caesar Cipher). For example,'A' becomes 'D', 'B' becomes 'E', 'Z' becomes 'C', and so on. Spaces and punctuationare not encoded; they remain unchanged.Alice wants to send the following message to Bob: "HELLO WORLD".a. Encrypt Alice's message using the specified shift. Provide the encrypted text.………………………………………………………………………………………………[1]b. Discuss the security of using the Caesar Cipher for encrypting messages.Consider scenarios where Eve knows or does not know the method ofencryption.……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………[1]

What is the main purpose of using "padding" in block cipher encryption?To speed up the encryption processTo ensure the message is a multiple of the block sizeTo provide additional keys for encryptionTo create a more complex encryption algorithm

Think of the alphabet: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z. If BAD = 10, DAC = 11, and CGI = 22. What is the value of PAD?

Question No. 1: (Marks 10) Suppose a Station A transmits a message containing five characters to Station B using Even Parity encoding to ensure data integrity during transmission. Each character consists of 8 bits encoded in the ASCII. Station B receives the message of five 9-bit data elements and needs to extract the 8-bit data message from each element and decode it using ASCII to form meaningful words. The data elements received by Station B are: Received 9-bit Data Elements: 010101100 010101010 010011001 010011010 010100110 Assuming the data is received correctly without any errors by Station B, you are required to do the following tasks: 1. Extract 8-bit Data Message: Remove the Parity bits to extract the 8-bit data message from each 9-bit received element. 2. Decode and Extract using ASCII: Convert each 8-bit data message into its corresponding ASCII character to extract the meaningful words. Give your answer in the following table: Received Message 010101100 010101010 010011001 010011010 010100110 Data message (Bits)? Decoded Message?