## Winter 2013 - Math 4161 3.0

Tuesday, Thursday  2:30-4pm  HNE 031

 Professor Mike Zabrocki Office: TEL 2028 Office Hours: Monday 12:30-2:30pm, Tuesday 4-5 (cancelled Jan 22 for dept meeting) or by appointment e-mail : web page: http://garsia.math.yorku.ca/~zabrocki course web page: http://garsia.math.yorku.ca/~zabrocki/math4161w13/ TA:

 Course 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 cryptography.

## Announcements:

(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 http://courseevaluations.yorku.ca.
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 at 9am.

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.