Mathematics of Cryptography
Winter 2013 - Math 4161 3.0
Tuesday, Thursday  2:30-4pm  HNE 031
Description :Cryptography deals with the study of making and breaking secret codes.
We will be studying situations that are often framed as a game between three
parties: a sender (e.g., an embassy), a receiver (the government office) and an opponent (a spy).
We assume that the sender needs to get an urgent message to the receiver through communication
channels which are vulnerable to the opponent. To do this communication, the sender and receiver
agree in advance to use some sort of code which is unlocked by a keyword or phrase. The opponent
will be able to intercept the message. Is he/she able to unlock the message without knowing the key?
In this course we will learn some probability theory, information theory and number theory to
answer questions about how vulnerable the methods of sending secrets are. This has a great number
of applications to internet credit card transactions, wireless communication and electronic
voting. We will start by learning some classical codes (used up through WWI) and analyzing
those. The last third of the course we will start to learn the methods that are used in modern
(January 28, 2013) A request for more practice problems was answered and I posted
6 more questions.
(January 20, 2013) I am going to have to cancel my office hours for January 22
because of a department meeting. If you were planning on coming, we can reschedule
for some time earlier in the day or sometime on Thursday.
(January 8, 2013) (RULE #1) I will NEVER EVER post solutions to practice questions or quizzes.
Don't ask. Email questions like
"what is the answer to number xxxx?" will mostly be ignored. I will answer questions
about the practice by email on an individual basis but I need to know what you
tried to solve the problem.
(February 26, 2013) The final exam schedule was announced yesterday.
Our exam is Monday, April 22 from 9am - 12pm in Room TEL 0005. $B$ there or $B^2$.
FYI, I am going to have to cancel office hours today because I have
a department meeting.
(March 18, 2013) I just received the following announcement:
The Winter 2013 and Fall/Winter 2012-2013 Course evaluations will be available
on-line tomorrow (March 19, 2013). The URL link is
Students should go on-line and complete the course evaluations.
They have from March 19, 2013 to April 4, 2013 to submit the evaluations.
Please encourage and remind your students to go on-line and complete the course evaluations.
(March 20, 2013) You should be able to access the moodle at http://webct.math.yorku.ca.
In order to sign in you should use your AML account.
If you have not registered for this account already then you may need to
do this through Manage My Services at MAYA.
(April 4, 2013) I will have office hours 3-4pm on Monday, April 15
and 10am-12pm on Wednesday, April 17. I have an exam Thursday April 18th in the evening
so I may be around for part of Thursday to answer questions but I won't set specific office
hours unless I am unable to meet demand on MW. The exam is the following Monday morning
Text : I will not be following a
textbook for the course. The last time I had a textbook I followed
class notes much closer than we followed
the book. The text that I used in the past was
'Cryptography: an introduction' by Nigel Smart. I was informed a few months
ago that this text is now out of print, but I am sure it is possible to find a few copies.
It is good because it seems to cover what I do in this course + more, however
I expect the notes will prove to be more useful and it is important that you come to class to
ask questions. FYI, the book does not cover the introductory material
on classical ciphers very well, but I like it.
Issues of Academic Integrity :
Your exams and quizzes will be
open books and notes. I want you to have access to reference material
when you are working. I expect you however to keep your eyes on your
own paper. Students are expected to be familar with
Policy on Academic Honesty and to follow it. The one time that I taught
this class I had at least two people pass through hearings with the administration
because of issues with academic dishonesty. This time I will not take chances
and I intend to put as many mesures into effect to stop cheating as possible.
Calculators that use + - * / ^ and log are allowed on quizzes and tests.
Calculators which have more advanced functions like
factor, gcd, Jacobi, mod and discrete log are not currently
commonplace and until those functions
are available to everyone I expect you to stick with a basic calculator.
No smart phones.
Books and notes are allowed on the tests and quizzes as well but I try to add
some creative way of making the problems unique so that they are not the same
as changing a few numbers from a practice problem.
It is not my job to watch over your shoulder to tell you the difference between right
and wrong. I give you a lot of leeway (e.g. open book and notes, and calculators)
in this class because I expect you to be honest and follow these rules and
not copy off of your neighbor when we have tests and quizzes.