opereting system (assignment #5)

timer Asked: Apr 25th, 2017

Question description

hi, plz answer the questions. Thanks

1. What is a covert channel? What is the basic requirement for a covert channel to exist? 2. In a full access-control matrix, the rows are for domains and the columns are for ob- jects. What happens if some object is needed in two domains? 3. Two different protection mechanisms that we have discussed are capabilities and ac- cess-control lists. For each of the following protection problems, tell which of these mechanisms can be used. (a) Ken wants his files readable by everyone except his office mate. (b) Mitch and Steve want to share some secret files. (c) Linda wants some of her files to be public. 4. Represent the ownerships and permissions shown in this UNIX directory listing as a protection matrix. (Note: asw is a member of two groups: users and devel; gmw is a member only of users.) Treat each of the two users and two groups as a domain, so that the matrix has four rows (one per domain) and four columns (one per file). – – – – rw–r– –r– – rwxr–xr – x rw–rw– – – – rw–r– – – – – 2 1 1 1 gmw asw asw asw Users Devel Users Devel 908 432 50094 13124 May 26 16:45 May 13 12:35 May 30 17:51 May 31 14:30 5. Break the following monoalphabetic cipher. The plaintext, consisting of letters only, is a well-known excerpt from a poem by Lewis Carroll. kfd ktbd fzm eubd kfd pzyiom mztx ku kzyg ur bzha kfthcm ur mfudm zhx mftnm zhx mdzythc pzq ur ezsszcdm zhx gthcm zhx pfa kfd mdz tm sutythc fuk zhx pfdkfdi ntcm fzld pthcm sok pztk z stk kfd uamkdim eitdx sdruid pd fzld uoi efzk rui mubd ur om zid uok ur sidzkf zhx zyy ur om zid rzk hu foiia mztx kfd ezindhkdi kfda kfzhgdx ftb boef rui kfzk 6. Name three characteristics that a good biometric indicator must have in order to be useful as a login authenticator. 7. Authentication mechanisms are divided into three categories: Something the user knows, something the user has, and something the user is. Imagine an authentication system that uses a combination of these three categories. For example, it first asks the user to enter a login and password, then insert a plastic card (with magnetic strip) and enter a PIN, and finally provide fingerprints. Can you think of two drawbacks of this design? 8. Describe how stack canaries work and how they can be circumvented by the attackers. 9. Why are rookits extremely difficult or almost impossible to detect as opposed to viruses and worms?

Tutor Answer

(Top Tutor) Studypool Tutor
School: Purdue University
Studypool has helped 1,244,100 students
flag Report DMCA
Similar Questions
Hot Questions
Related Tags
Study Guides

Brown University

1271 Tutors

California Institute of Technology

2131 Tutors

Carnegie Mellon University

982 Tutors

Columbia University

1256 Tutors

Dartmouth University

2113 Tutors

Emory University

2279 Tutors

Harvard University

599 Tutors

Massachusetts Institute of Technology

2319 Tutors

New York University

1645 Tutors

Notre Dam University

1911 Tutors

Oklahoma University

2122 Tutors

Pennsylvania State University

932 Tutors

Princeton University

1211 Tutors

Stanford University

983 Tutors

University of California

1282 Tutors

Oxford University

123 Tutors

Yale University

2325 Tutors