Venue: The class meets Tuesday and Thursday from 8:35 am to 9:50 am in 109 Pratt and Friday from 1:15 pm to 2:05 pm in 216 Skinner. Text: There are two textbooks for this course: Thomas H. Barr, Invitation to Cryptology, Prentice-Hall, 2002; and Simon Singh, The Code Book, Anchor Books, 2000. Course description: We will begin with a study of classical cryptography, covering various substitution and transposition ciphers and some of the mathematics that has been used in their cryptanalysis. We will then develop enough basic number theory to understand the basics of contemporary cryptography, including public-key cryptography. Homework: There will be a problem set each week. Problem set solutions will be graded for presentation as well as correctness. Exams: There will be two hour exams during the semester, probably during the weeks of March 3 and April 14. Quizzes: Except in exam weeks, there will be a ten-minute quiz each week. Grading: Your lowest problem-set grade and your two lowest quiz grades will be dropped, and your course grade will be computed as follows: Problem Sets   40% Quizzes 20% Hour Exams 20% Final Exam 20% Resources: My office hours are listed on my web page; you are welcome to make appointments to talk with me at other times. The Honor Code: You are encouraged to collaborate on problem sets, but only as long as the information flow goes both ways. Each student must write up her own solutions independently. Direct copying from another student's paper will be treated as a violation of the honor code. No collaboration will be permitted on the quizzes, the hour exams, or the final exam.