Question 17 (1 point) RSA derives a key pair using the discrete logarithm problem (DLP). O O True False Question 18 (1 point) In an ____________ attack, a large number of machines are used to interrupt a service or take down a system. Question 19 (1 point) What of the following involves gaining sensitive information from personal contact with an employee? O Phishing Social Engineering Drive-by-download O Zero-day vulnerability Ransomware Question 20 (1 point) Suppose that you have created a file in a Linux machine and the file has the permission of 650. What will be the value of umask? Question 21 (6 points) BASTION Inc. has changed their encryption practice from AES-128 to AES-256. Suppose that you happen to eavesdrop their network traffic and try to launch a brute-force attack with a ciphertext you have grabbed from the eavesdropping. Compared to a brute-force attack on AES-128, how many MORE attempts do you need to try to launch the same attack on AES-256? Question 22 (5 points) Consider a brute-force attack on DES which uses a key of 64 bits, out of which every 8th bit is used to check the validity of the key. Let's assume that it takes 1 nanosecond to try a single key. How much time in years and days will it roughly take to launch your attack successfully in the worst case