RC4 Stream Cipher Overview Answers 1. What is the primary method of encryption used in the RC4 cipher? A. Using a block cipher to rearrange data. B. Substituting each byte with a corresponding byte from a static table. C. XORing the plaintext with a generated key stream. D. Applying a mathematical function to the plaintext. Answer: XORing the plaintext with a generated key stream. (C) RC4 uses the process of XORing the plaintext with a dynamically generated key stream for encryption. 2. What is the purpose of the Key Scheduling Algorithm in RC4? A. To initialize a state table based on the secret key. B. To store the generated key stream securely. C. To encrypt the plaintext before sending it. D. To generate multiple keys for different sessions. Answer: To initialize a state table based on the secret key. (A) The Key Scheduling Algorithm initializes a 256-byte state table based on the provided secret key. 3. What is a major flaw that affected the security of RC4? A. It relies on complex mathematical transformations. B. Limited key streams could lead to predictable output. C. The algorithm uses a very long key length. D. The encryption process is too slow for practical use. Answer: Limited key streams could lead to predictable output. (B) A significant security flaw in RC4 was its use of relatively short key streams, which could exhibit patterns. 4. How is the key stream generated in RC4? A. By using independent random number generators. B. Through a simple iterative addition of key bytes. C. By applying fixed transformations to the plaintext. D. Through complex swapping operations within a state table. Answer: Through complex swapping operations within a state table. (D) The key stream in RC4 is produced via complex swapping operations in the initialized state table. 5. Which property of the XOR operation is crucial for decryption in RC4? A. XORing creates a unique result that cannot be reversed. B. XORing a number with 0 returns the number unchanged. C. XORing a number with itself produces a zero value. D. XORing two different values produces a predictable result. Answer: XORing a number with itself produces a zero value. (C) XORing a value with itself returns 0, which allows for recovering the original plaintext when decryption is performed. 6. What is a critical component to avoid when using the RC4 algorithm? A. Using very large keys. B. Employing a short key length. C. Generating the same key stream multiple times. D. Implementing complex mathematical models. Answer: Generating the same key stream multiple times. (C) Key stream generation in RC4 should prevent repetition to enhance security. 7. Which of the following best describes RC4's operational speed? A. It operates significantly slower than traditional block ciphers. B. It is fast and efficient for real-time data encryption. C. It requires extensive computational resources. D. Speed varies greatly depending on the key length. Answer: It is fast and efficient for real-time data encryption. (B) RC4 is known for its speed and simplicity, making it efficient for real-time data encryption. 8. Why has RC4 been deprecated in many contexts? A. Its encryption speed is not sufficient. B. It is too complicated for implementation. C. It is no longer compatible with modern applications. D. There are stronger algorithms available for encryption. Answer: There are stronger algorithms available for encryption. (D) Due to significant cryptographic weaknesses, stronger encryption algorithms have replaced RC4 in many applications.