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Yale University Department of Computer Science
Michael J. Fischer

CS 467: Cryptography and Data Security

Announcements, Spring 2005

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Announcements will appear for awhile on the course home page and then be archived here.

  • 25 Apr. The TA will hold a review session on Tuesday, April 26, at the regular class time, 4:00-5:15 pm. Assume it will be in the usual classroom, AKW 200, unless I announce otherwise.

  • 23 Apr. I've posted solutions to PS6 (.pdf or .ps).

  • 20 Apr. Here are slides on Kerberos, SSH and SSL (.pdf).

  • 18 Apr. I've posted solutions to PS5 (.pdf or .ps).

  • 17 Apr. I've updated lecture notes for week 11 (.pdf or .ps) and week 12 (.pdf or .ps). Changes are mostly minor, but some technical errors were fixed, and a little new material was added to week 11.

  • 16 Apr. Problem set 7 (.pdf or .ps) is available. Solutions should be submitted electronically or placed in the TA's mailbox (AKW 311) by 5:30 pm on Monday, April 25. I will grant an automatic penalty-free 2-day extension to all who request it. However, I encourage you to start early on this assignment and to allow extra time. In any case, no work will be accepted after the end of reading period, with or without late penalty, except when authorized by the dean.

  • 15 Apr. Handout 18 gives a more complete treatment of pseudorandom sequence generation than is found in the lecture notes.

  • 8 Apr. Correction to problem set 6: I've eliminated one of the problems from the version posted a few minutes ago. The current version 2 has only three problems. Please discard the original if you happened to have download it during that interval.

  • 8 Apr. Problem set 6 (.pdf or .ps) is available. Solutions should be submitted electronically or placed in the TA's mailbox (AKW 311) by 5:30 pm on Friday, April 15.

  • 3 Apr. I've updated lecture notes for week 9 (.pdf or .ps), week 10 (.pdf or .ps), and week 11 (.pdf or .ps). Changes are mostly to shuffle material around to better match the actual lectures, but there are some corrections of errors and a little new material.

  • 2 Apr. I've posted solutions to PS4 (.pdf or .ps). There was some difficulty with the grading of the second part of problem 12. If you lost points on this part but think your answer was correct after reading the solutions, then please contact the TA for a grade adjustment.

  • 31 Mar. Problem 17 should refer to "strong collision-free hash functions", not "one-way hash functions". Version 2 of problem set 5 (.pdf or .ps) corrects this problem. Sorry for the error.

  • 28 Mar. Problem set 5 (.pdf or .ps) is due in class on Tuesday, April 5.

  • 22 Mar. Classroom changed again. We'll be in AKW 200 as usual. Sorry for the confusion.

  • 13 Mar. Another error in PS4, this time with Problem 14! DSA uses two primes, p and q. Both need to be written to and read from the public and private key files. Version 2 of the handout correcting this error is now on the web site, replacing the previous version.

  • 4 Mar. (12:30 am) Oops! I found a few errors in PS4 after posting it. If you downloaded it between midnight and 12:30 am, please download it again.

  • 4 Mar. Problem set 4 (.pdf or .ps) is due in class on Thursday, March 24. This requires some computer programming. Programs should be submitted online. Written answers can be submitted online or on paper.

  • 2 Mar. Change of classroom notice. On Tuesday, March 22, class will be held in AKW 500 instead of in our usual classroom. Please make note of this change.

  • 2 Mar. I've made a minor update to week 7 lecture notes and fairly extensive revisions to week 8 lecture notes.

  • 2 Mar. I've posted the questions (.pdf or .ps) from last Thursday's midterm examination and the solutions (.pdf or .ps).

  • 1 Mar. I've posted solutions to PS3 (.pdf or .ps).

  • 27 Feb. I've updated lecture notes for weeks 4, 5, and 7 and added initial drafts of notes for the remaining weeks of the course. Links are on the Lecture Notes page.

  • 22 Feb. I've posted a study guide (.pdf or .ps) for your use in preparing for the midterm exam.

  • 22 Feb. Revision 3 of week 6 lecture notes corrects an error in the proof of Claim 4 in Section 6.5. Thanks to Alex Hetherington for pointing this out to me.

  • 21 Feb. The Yale Bookstore has asked me to announce that unsold textbooks will be returned to the publishers after midterms. They say that "large numbers" of our textbook, Modern Cryptography, remain on the shelf. If you were planning on buying the book (recommended) and haven't gotten around to it, now's the time to do it.

  • 21 Feb. Revised week 6 lecture notes and preliminary week 7 lecture notes are available.

  • 21 Feb. New handouts posted:

    1. Solutions to PS1 (.pdf or .ps).
    2. Solutions to PS2 (.pdf or .ps).
  • 21 Feb. Correction to yesterday's announcement concerning exam coverage: I should have included the material in problem set 3 also since it is based on the first six weeks of lectures.

  • 20 Feb. The TA will hold a review session for the midterm exam on Tuesday evening, February 22, 8:00-9:00 pm, in AKW 100 (if available, or in AKW 200, 400, or 500 if not).

  • 20 Feb. The midterm exam will cover all of the material covered in the first six weeks of class, that is, through last Thursday, February 17, as well as the material covered in problem sets 1 and 2.

  • 18 Feb. Problem set 3 (.pdf or .ps) is a "mini" problem set to give you some practice before the midterm exam with some of the recently-covered number theory. It is officially due in class on Tuesday, February 22, but I will give an automatic 2-day extension to anybody who requests it. Nevertheless, I encourage you to finish these problems by the due date.

    Reminder: Midterm exam on February 24.
    (See 19 Jan. announcement.)

  • 16 Feb. Revised week 5 lecture notes and preliminary week 6 lecture notes are available. A few links still need fixing in week 5, but I thought it better to get what I have finished up on the web now.

  • 10 Feb. Problem set 2 (.pdf or .ps) is due in class on Thursday, February 17. This requires some computer programming. Programs should be submitted online. Written answers can be submitted online or on paper.

  • 10 Feb. Three new handouts have been posted to the web. The are supplements to the lecture notes and to the material in the textbook. They are

    • Number theory summary (.pdf or .ps)

    • Linear congruence equations (.pdf or .ps)

    • The Legendre and Jacobi symbols (.pdf or .ps)

  • 10 Feb. The TA has set up a discussion bulletin board for this course. It already has some information on using ln3. Check it out!

  • 6 Feb. Problem 1 requires finding the unknown invertible key matrix used by the Hill cipher to generate the ciphertext. Inverting matrices is generally done using Gaussian elimination. However, in this case, all arithmetic is being done modulo 26. Since 26 is not prime, not all non-zero elements mod 26 have inverses. In particular, 13 and even numbers all fail to have inverses mod 26. This causes Gaussian elimination to fail on some invertible matrices.

    A fix is to decompose the ring of integers modulo 26 into the direct product of the field of integers modulo 2 and the field of integers modulo 13. The matrices are inverted separately over these two fields and then recombined to yield the inverse modulo 26. We will be covering the theory needed to understand these steps in the next few weeks. In the meantime, I have written a matrix inversion program and placed it on the Zoo in /c/cs467/assignments/ps1/matinvert for your use. You can also access these files via the web.

  • 5 Feb. Revised week 4 lecture notes and preliminary week 5 lecture notes are available. (Week 5 are in pdf/ps formats only.)

  • 4 Feb. I put a link to the DES standard DES standard at the bottom of the resources page.

  • 4 Feb. I installed Professor Eisenstat's online submission scripts in the Zoo. They are located in the course directory, /c/cs467/bin. Click here for brief documentation on how to use them. You must have a cs467 course account to use them. See the syllabus for instructions on how to sign up for a course account.

  • 3 Feb. TA office hours have been extended as shown below.

  • 3 Feb. Problem set 1 (.pdf or .ps) is due in class on Thursday, February 10. Stay tuned for instructions on optional on-line submission.

  • 1 Feb. Revised week 3 lecture notes and preliminary week 4 lecture notes.

  • 27 Jan. TA office hours contact information and office hours are shown below.

  • 20 Jan. Lecture notes for the first three weeks of the course have been posted. These notes are a work in progress and will be revised from time to time as the term goes on. So that you can tell whether a printed version is up to date or not, I will include a revision number on each. Later revisions obsolete earlier ones. You will see that the week 1 and week 2 notes are already in their 2nd revision, and that some of the material formerly in week 2 has been moved into week 3.

  • 20 Jan. Below are pictures of two cryptography devices mentioned in class.

    photo
    Jefferson wheel
    photo
    Enigma rotor machine
  • 19 Jan. There will be one 75 minute midterm examination instead of the two "hour exams" mentioned in the syllabus. It will be held on February 24 at the regular class time and place.


  • 11 Jan. Final examination will be at the officially scheduled time, Saturday, May 7, 2:00 pm.

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Chameleon.


Last modified: Sat Apr 30 13:00:57 EDT 2005

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