Suppose that someone suggests the following way to securely confirm that the two of you are both in possession of the same secret key. You create a random bit string the length of the key, XOR it with the key, and send the result over the channel. Your partner XORs the incoming block with the key and sends it back. You check, and if what you receive is your original random string, you have verified that your partner has the same secret key. Is this scheme secure?

Write a program that prompts the user to input a string. the program then uses the function substr to remove all the vowels from the string. for example, if str = "there", then after removing all the vowels, str = "thr". after removing all the vowels, output the string. your program must contain a function to remove all the vowels and a function to determine whether a character is a vowel.

Answer the following questions regarding your system by using the commands listed in this chapter. for each question, write the command you used to obtain the answer. a. what are the total number of inodes in the root filesystem? how many are currently utilized? how many are available for use? b. what filesystems are currently mounted on your system? c. what filesystems are available to be mounted on your system? d. what filesystems will be automatically mounted at boot time?

Acomputer has a two-level cache. suppose that 60% of the memory references hit on the first level cache, 35% hit on the second level, and 5% miss. the access times are 5 nsec, 15 nsec, and 60 nsec, respectively, where the times for the level 2 cache and memory start counting at the moment it is known that they are needed (e.g., a level 2 cache access does not even start until the level 1 cache miss occurs). what is the average access time?