For Lecture, Monday, April 9th (Authentication)

In preparation for this lecture on authentication, please read chapter 6, sections C, D, and E.

For Recitation, Tuesday, April 10th (Trusting Trust)

To prepare for the recitation, read Ken Thompson's "Reflections on Trusting Trust". Do not be deceived by the shortness of this paper -- it is very deep and requires a lot of thinking and understanding, but it is also fun, once you get the hang of it. This paper exemplifies the qualities you should be striving for in your own papers: content, clarity and conciseness. Keep this in mind as your prepare a one-pager based on the following question:

Most cryptographic protocols are judged by the security they offer between principals -- participants in the protocol, often referred to in analyses as "Alice", "Bob", "Carol", etc. Although in practice the principals of interest are the users, analyses often overlook this; "Alice" represents a computer. This abstraction, while convenient, may undermine the security of systems for e-commerce, digital cash, electronic voting, and even basic secure communication.

What security risks does this abstraction overlook? Consider Alice and her computer in terms of the kinds of attack described in Thompson's article. What risks is the person named Alice exposed to? What other attacks, not mentioned, and exploiting this abstraction, are possible? Can you invent ways to thwart them?

For Lecture, Wednesday, April 11 (Authorization)

In preparation for this lecture, read section F of chapter 6.

For Recitation, Thursday, April 12 (Why Crypto Systems Fail)

Here is the hands-on assignment due today:

The goal of this hands-on is to give an introduction to web certificates and how they achieve their goal of authentication. MIT uses certificates to authenticate you to systems such as WebSIS (http://student.mit.edu). We are going to try and understand both the concepts and practice of how this works. Helpful URLs include http://web.mit.edu/is/help/cert/ and http://www.rsalabs.com/faq/.

1. Obtain an MIT Certificate

   If you have not already done so, please obtain an MIT Certificate from https://ca.mit.edu/. You will need to use Netscape for this to work; The Netscape available on Athena will work.

2. Secure access instructions

   Read the following page: Limited and secure access to web content over https.

3. Web page setup

   Set up a web page in your Athena directory that is accessible only to you, one other athena user (a partner of your choosing for this assignment), and to the teaching assistant for your section. Verify the following two conditions:

   a) Your partner can reach the page with a web browser, using an MIT-issued personal certificate. If you have set up the permissions properly, your TA should also now be able to access the page. (If your partner attempts to access the page from an Athena workstation, make sure they use the page's network URL -- e.g., https://web.mit.edu/$USER/www/assignment6.html -- to ensure that the certificate mechanism is exercised.)

   b) At least one person other than your TA or partner fails to reach the page from a web browser even though they present their MIT-issued personal certificatxse.

   So that your teaching assistant can also try it out, leave the restricted web page set up until you get your paper back.

   In the answer to this question, list the URL of the page you created and include the .htaccess.mit file you used to create the permissions.

4. Trust considerations

   When you connect to a secure site, your browser will typically inform you of this. You can verify this by looking at the Document Info for the page in question (by pressing the Security button). How do you know that you have actually connected to the correct site and not to an imposter? Consider what a certificate actually certifies, what components comprise it, etc.

   Make a list of everything that you must trust in order to be confident that your web page really is accessible to noone else.

Monday-Tuesday, April 16-17

Patriots' Day weekend. No classes. Enjoy the Boston Marathon.

For Lecture, Wednesday, April 18 (Certification)

In preparation for this lecture, read section G of chapter 6.

Review session for the second quiz will be in Rm 34-101 from 7-9pm.

For Recitation, Thursday, April 19

Read chapter 6 appendix B, "Secure Socket Layer (SSL)".

For Quiz 2: Friday, April 20

Quiz 2 will be held from 2-3pm on Friday, April 20, 2001. This quiz will cover all material presented in L9 (Network Layers) through R17 (Why Crypto Systems Fail). The quiz will be open book. That means you can bring along any printed or written materials that you think might be useful. Calculators are allowed, though not necessary. The quiz will be multiple choice, similar to quiz 1. Practice problems can be found in section 10 of the notes, which was handed out as part of update 1.11. The quiz will be held in 34-101 and in Walker (50-340). See the chart below to determine which location you should go to for the quiz.

            Last Name      Location
              A-M           Walker
              N-Z           34-101

The quiz is being held in a regularly scheduled class hour. The date was announced at the beginning of the term, so you should not have problems with scheduling conflicts. If, nevertheless, you have managed to create a conflict, contact Prof. Kaashoek at kaashoek@mit.edu as soon as possible to resolve the problem.

System aphorism of the week

The price of reliability is the pursuit of the utmost simplicity.
      -- Charles Anthony Richard Hoare, "The emperor's old clothes" (1980)