Overview
Official summary:
Studies the design and use of cryptographic systems for
communications and other applications such as ecommerce. Discusses
the history of cryptographic systems, the mathematical theory behind
the design, their vulnerability and the different cryptanalytic
attacks. Topics include: stream ciphers such as shift register
sequences; block ciphers such as DES and AES; publickey systems such
as RSA, Discrete Logarithms; signature schemes; hash functions such
as MD5 and SHA1; protocol schemes such as Identification schemes,
ZeroKnowledge proofs, Authentication schemes and Secret Sharing
schemes. Key management problems including NeedhamSchroeder
protocols and certificates will be discussed.
Announcements
Fri, 11 Dec 2009: The slides from the second day of presentations are up.
Thanks to all the presenters, and thanks to everyone for a nice
semester.
Remember that the final paper is due this coming Monday  the 14th.
Thu, 10 Dec 2009: The slides for the first day of presentation are up.
Wed, 09 Dec 2009: Slight revision to the presentation schedule.
Mon, 07 Dec 2009: The preliminary presentation schedule can be found here.
Thu, 03 Dec 2009: Slides for the lecture on secure multiparty computations are up.
Thu, 19 Nov 2009: Slides for the lecture on zero knowledge protocols are up, including a
couple of corrections following class discussions.
My plan is to send you all papers for your projects on Friday
night. Stay tuned.
Thu, 12 Nov 2009: Slides for the lecture on key establishment protocols are up. Homework
7 is out, due next Thursday. Also remember that I'd like to see your
proposal about what you would like to
investigate for your final project by November 15.
Tue, 10 Nov 2009: You can find a small writeup about the final
project here. I
would like to see your proposal about what you would like to
investigate for your final project by November 15. An email will do fine.
Thu, 05 Nov 2009: Slides for the lecture on security protocols are up, including
those I skipped over, on protocols with publickey cryptography
and Kerberos. Homework 6 is out, due next Thursday.
Thu, 05 Nov 2009: Some of you had a question about question 2 of homework 4, about how
to get the value of a. If you follow the technique in the book,
you end up with an equation to solve that doesn't seem to be easily
solvable. In particular, you want to solve ax = b (mod n) for x,
provided you know gcd(a,n)
divides b  in which case you know there's a solution.
The trick is to reduce this equation to an equation of the form a'x =
b' (mod n') with gcd(a',n') = 1, because for that you can find a
solution easily.
One approach is to take d=gcd(a,n), and take a'=a/d,
b'=b/d, and
n'=n/d. You then solve a'x = b' (mod n'). Note that gcd(a',n')=1.
You get a solution, call it s, but that's a solution mod n'.
The trick
then is to convert this s to a solution of the original equation, mod
n. I'll leave you to figure out how to do that. Hint: think about what
values (mod n) give you s (mod n'). Another hint: there are
d=gcd(a,n)
of them.
Thu, 29 Oct 2009: Slides for the lecture on secret sharing are up. Homework 5 is out,
due next Thursday. Reading assignment for next class: chapter 13,
sections 1 and 2. Stay tuned tomorrow night for a list of ideas for
the end of term project.
Wed, 21 Oct 2009: Blackboard is giving me grief, and somehow does not always
consistently show all grades that I have entered. I believe (big
caveat) that I have corrected the problem, and that you should see all
the grades that I have for you. If you believe this is mistaken and
that I am missing something, let me know.
Tue, 20 Oct 2009: Lei points out that in the list of chapters/sections I gave earlier, I
included the subsection about the ECDSA signature scheme, the version of
DSA based on elliptic curves. You do not have to know/read that one,
since after all I had you skip the section on elliptic curves
cryptography. (I do not know exactly what subsection it is, but I
believe it's one of those in 7.3 or 7.4.)
Sat, 17 Oct 2009: Grades for all homeworks (except for one or two that I still need to
get to because of printing problems) can be found
on Blackboard. Grades are on
a perquestion basis (each out of 10). Graded homeworks have been put
outside my office door, but not those that were submitted online and
containing source code. If you have any question as to your grade on a
question and you do not have a hardcopy of the homework, feel free to
shoot me an email. I will try to print out an explanatory sheet for
every homework that was submitted online that I will add to the pile
of graded homeworks come Monday.
Fri, 16 Oct 2009: The midterm next week will be in class, and will be open notes and
open books. No computers or smartphones. But you can bring a
calculator if you really want to. The midterm will cover all the
lectures we have seen until yesterday, including signature schemes. In
the textbook, you will be responsible for the following
chapters/sections:
Chapter 1 [sections 1.1, 1.2 (only 1.2.11.2.3)]
Chapter 2 [sections 2.12.7]
Chapter 3 [sections 3.13.2, 3.53.7]
Chapter 4 [sections 4.1, 4.2 (only 4.2.1), 4.3 (only 4.3.1), 4.4]
Chapter 5 [sections 5.15.3]
Chapter 6 [section 6.1]
Chapter 7 [sections 7.17.4]
Fri, 16 Oct 2009: Slides for the lecture on signature schemes are up. Homework 4 is out,
due next Thursday. Reading assignment for next class: reach chapter 7
in Stinson. Note that next Thursday is the midterm; I will post some
more information about the midterm later tonight, including
chapters/sections of the textbook to study.
Fri, 09 Oct 2009: Slides for the lecture on hash functions are up. Extension for
homework 3 has been granted until Sunday night. Reading assignment for
next class: read chapter 4 in Stinson.
Thu, 01 Oct 2009: Slides for the lecture on publickey cryptosystems are up.
Homework 3 is out, due next Thursday.
Reading assignment for next class: read chapters 5 and 6.
Thu, 01 Oct 2009: If you need an extension for homework 2, I am happy to give you an
extension until the end of the weekend, that is, until Sunday
night. Send me an email to let me know.
Thu, 01 Oct 2009: For homework 2 submissions, please send me an email containing your
source code packaged in either a zip file or a tar/gz file, and sample
executions.
Mon, 28 Sep 2009: I completely forgot to update this website with my office hours, sorry
about that. They're Thursday 16h0018h00 (before class, then), and my
office is 328 WVH.
Thu, 24 Sep 2009: Slides for the lecture on block ciphers are up.
Homework 2 is out, due next Thursday.
Finally, reading assignment for next class: read chapter 3.
I will try to put up some sample plaintexts and ciphertexts to check
your DES code for homework 2.
Mon, 21 Sep 2009: Slides for the second lecture are up. They have a colored background
unfortunately, so I recommend not printing them unless you want to
kill your printer. It's not that easy to make a noncolored copy from
those, so I won't even bother. Besides, everything is contained in
Chapter 2 of Stinson anyways, in some form or another. I also posted
the first homework, due next lecture. I also added links to two text
files with the content of the ciphertexts for question 2, in case you
want to attempt decryption using a program you wrote.
Thu, 10 Sep 2009: Slides for the first lecture are up. The link is in the schedule
below. I've also put a pointer to the short story I mentioned in
class, Poe's "The Gold Bug". Reading assignment for next week: chapter
1 of Stinson.
Mon, 07 Sep 2009: Setting up the RSS feed for the course. You should see an RSS link up
in your browser.
Course Information
Time and Location:
Thursdays 18h0021h00 in 011 Kariotis Hall (#35)
Instructor: Riccardo Pucella,
328 West Village H (#23H)
Office hours: Thursday 16h0018h00
Teaching Assistant: None
Course Web Site: http://www.ccs.neu.edu/home/riccardo/cs6750
Prerequisites: CS 5800 or CS 7800 (can be taken concurrently)
Grading: Grading will be based on homeworks (about one a
week), a
midterm, and either a final exam or a final project:
 Homeworks: 50%
 Midterm: 25%
 Final exam or project: 25%
This scheme is subject to change until the first lecture.
Textbooks:
The textbook for the course is:
You may also find the following book useful, but it is not required:
Schedule Outline and Lecture Notes
This schedule is subject to change without warning. Readings
will be assigned to supplement lectures, and posted here.
Project Presentations
December 10th
Student  Topic  Notes 
Katelyn Berry 
BraidBased Cryptography 
 Slides

Matthew Ellis 
EllipticCurve Cryptography 
 Slides

Sergey Grabkovsky 
Steganography 
 Slides

Jessica Lowell 
Neural Cryptography 
 Slides

Xiaohai Yu 
Hashing for Page Sharing 
 Slides

Nicholas Whalen 
Anonymity 
 Slides

Lei Qin 
Mobile IPv6 Security 
 Slides

December 11th
Student  Topic  Notes 
Creence Lin 
Electronic Cash 
 Slides

Srinivas Nama Jayakumar 
Secure HTTP 
 Slides

Amit Shinde 
Kerberos 
 Slides

YiHsun Lai 
Interaction between IPv4 and IPv6 
 Slides

Harsha Suleballe Jagadish 
PKIs and Risks 
 Slides

Mohinish Vinnakota 
SDSI ans SPKI 
 Slides

Homeworks
