PU Computer Science Questions

8. Represent the ownerships and permissions shown in this UNIX directory listing as aprotection matrix. (Note: asw is a member of two groups: users and devel; gmw is amember only of users.) Treat each of the two users and two groups as a domain, sothat the matrix has four rows (one per domain) and four columns (one per file).– rw– r– – r– – 2 gmw users 908 May 26 16:45 PPP– Notes– rwx r– x r– x 1 asw dev el 432 May 13 12:35 prog1– rw– rw– – – – 1 asw users 50094 May 30 17:51 project.t– rw– r– – – – – 1 asw dev el 13124 May 31 14:30 splash.gif21.Suppose that two strangers A and B want to communicate with each other using secret key cryptography, but do not share a key. Suppose both of them trust a third party Cwhose public key is well known. How can the two strangers establish a new sharedsecret key under these circumstances23. Natural-language text in ASCII can be compressed by at least 50% using various com pression algorithms. Using this knowledge, what is the steganographic carrying capaci ty for ASCII text (in bytes) of a 1600 × 1200 image stored using the low-order bits ofeach pixel? How much is the image size increased by the use of this technique (assum ing no encryption or no expansion due to encryption)? What is the efficiency of thescheme, that is, its payload/(bytes transmitted)