
Ezra Brown Office: 568 McBryde Office Phone: 2316950 Home Phone: 5529563 (before 9 PM) Email: ezbrown@math.vt.edu  Office Hours: Mon: 910, 34 Tue: 45 Wed: 2:203:20 Thu: 11:1512:15, 34 and by appointment 
Time and Place: 1:25 to 2:15 p.m. Mondays, Wednesdays and Fridays, McBryde 304
Text: Cryptography: Theory and Practice (3rd edition) by D. R. Stinson.
Topics: Two major issues in cryptography are key management and authentication, i.e. constructing and transmitting keys in a secure manner and ensuring that the recipient can tell the identity of the sender. Public Key Cryptography was originally developed to deal with these two issues. Topics include an introduction to public key cryptography, the RSA Public Key Cryptosystem, factoring and primality testing, the DiffieHellman Key Exchange, the ElGamal Public Key Cryptosystem, the discrete log problem, digital signatures, secret sharing, elliptic curve cryptosystems, and hash functions. These correspond to material from Chapters 5, 6, 7, 13, and 4 of the text, as well as occasional handouts for material not treated in the text.
Prerequisites for this course, and About Those Prerequisites: Math 4175 is prerequisite for Math 4176. Note that Math 4175 requires at least one mathematics course at or above the 3000 level, as well as knowledge of either a programming language (e.g. C, C++, Java) or a computer algebra system (e.g. Mathematica, Maple, or Magma). The material in Math 4175 was taken from Chapters 13 of the text as well as supplemental material on the ENIGMA machine, and includeds some number theory and permutation theory. It is DANGEROUS to take Math 4176 without first satisfying the prerequisites!
Evaluation: There will be two midterm tests, each worth 20% of your grade. these tests are tentatively scheduled for February 24 (Friday) and April 17 (Monday). There will be regular problem sets, worth 40% of your grade. A problem set is late after the end of class on the day it is due; late problem sets count zero. The final exam is worth 20% of your grade, and is scheduled for Tuesday, May 9 from 3:25 p.m. to 5:25 p.m. in McBryde 304. Giving or receiving assistance on the tests or final exam (except that specified by the instructor) is a violation of the honor code.
The ShanksTonelli modular squareroot algorithm
Problem Sets Policy: Problem sets are to be typed, either in LaTeX or using a word processor that has mathematical symbols. Include the statement of each problem before giving your solution. Hand your problem set in flat, stapled in the upper lefthand corner, and with your name, the date, and the problem set number in the upper righthand corner. On problems in which you write a program or use a CAS to solve, submit a printout of your source code or CAS code along with the output. Once again, forty percent of your grade is based on the problem sets.
Academic Honesty in Math 4176: On all assignments and exams it is expected that the student's submitted work reflects the student's own understanding of the problem(s) expressed in the student's own words. Unless given permission by the instructor, internet searches and all other outside sources  in particular, WolframAlpha  are strictly forbidden. Discussion of homework problems with other students and with the instructor is highly encourage. However, you should never consult anyone else's written solution to any homework problem.
The only assistance permitted on exams is clarification from the instructor.
Late Work and Test Policy: Homework is to be submitted inclass. A problem set is late after the end of class on the day it is due. Late problem sets count zero. Do not attempt to hand in homework by email, sliding it under my office door, to my department mailbox, etc.
I do not give makeup tests; however, I will substitute your final exam grade for at most one of your inclass tests, if such a substitution is to your advantage. You may not make up a missed final exam.
Grading: A percentage grade of 90, 80, 70 or 60 on any piece of work guarantees you a grade of A, B, C or D, respectively. Plusses and minuses are judgment calls and not subject to debate. Graduate students should note that the Graduate School converts any grade below C to an F.
University Statement on the Honor Code: The Undergraduate Honor Code pledge that each member of the university community agrees to abide by states:
"As a Hokie, I will conduct myself with honor and integrity at all times. I will not lie, cheat, or steal, nor will I accept the actions of those who do."
Students enrolled in this course are responsible for abiding by the Honor Code. A student who has doubts about how the Honor Code applies to any assignment is responsible for obtaining specific guidance from the course instructor before submitting the assignment for evaluation. Ignorance of the rules does not exclude any member of the University community from the requirements and expectations of the Honor Code. For additional information about the Honor Code, please visit the University Honor System website.
IMPORTANT MESSAGE!! If you are not on the class roll that comes out after the last add date, immediately check your schedule at a terminal and start attending the proper section. For no forseeable reason (computer and registrar personnel mistakes included) will you be allowed to stay in the wrong section or to drop a section for which you are actually enrolled after the last drop date. By simply attending a section you will not be placed on its roll.