CS 355 Class

Instructor: Samuel S. Wagstaff, Jr.

Phone: 49-46022; E-mail: ssw@cs.purdue.edu

In the event of a major campus emergency such as an epidemic of H1N1 flu, course requirements, deadlines and grading percentages are subject to changes that may be necessitated by a revised semester calendar or other circumstances beyond the instructor's control. Any such changes will be recorded on this web page.

Prerequisites: CS 251 and MA 351 (or equivalents).

The real prerequisites for CS 355.

Texts: (Don't buy any books until the first class meeting.)

Required:

Introduction to Cryptography with Coding Theory, second edition, W. Trappe and L. C. Washington, Prentice Hall, 0-13-186239-1

Recommended:

The Code Book, S. Singh, Random House, 0-389-49532-3

The overall course policies are the same as Spaf's.

Location and Time: REC 108, Tue-Thu 1:30-2:45.

Office: LWSN 1167; Office hours: Tuesday 4:30-5:30 PM, Thursday 3-4 PM.

Grading: Homework: 20%; Midterm exam 20%; Projects 20%; Final exam 40%.

Teaching Assistant: Aditi Gupta, Email: gupta21@cs.purdue.edu .

Office hours of Teaching Assistant: Wednesday 2:30 - 4:00 PM, LWSN B116J.

Link to a list of web sources on cryptography and security.

See also here for the new Advanced Encryption Standard algorithm Rijndael.

Day-by-day list of topics covered.

slides from an old lecture.

Transposition ciphers and substitution ciphers, IC.

Substitution ciphers, product ciphers.

Divisibility, Arithmetic with large integers, GCD.

Prime numbers.

Congruences: Definition and single linear ones.

Congruences for fun and profit.

Examples of the Extended Euclidean Algorithm and the Chinese Remainder Theorem

Fermat, Euler, fast exponentiation, finding large primes.

Block, stream ciphers, LFSRs, meet-in-the-middle attacks.

AES and Rijndael.

More about AES in comics.

Diffie-Hellman key exchange, discrete logs, P-H, RSA, ElGamal, Massey-Omura ciphers, RSA signatures, ElGamal public-key cryptosystem, Mental poker and quadratic residues.

Chinese remainder theorem, Solving quadratic congruences, Oblivious transfer and Zero-knowledge proofs.

MACs and Hash functions.

More about hash functions.

Threshold schemes, Digital Signature Standard and Subliminal Channels.

Construction of large primes.

PGP.

Key exchange algorithms.

Kerberos.

Signing contracts by e-mail.

Digital cash.

More about Digital cash.

All regrading of homework, midterm exams and projects must be done within two weeks after the work is returned to the class.

Please use a word processor to format your homework solution.

Homework # 1, due Tuesday, September 15, 2009, 1:30 PM, on paper, in class. In questions 2 and 3, your reasoning is much more important than the numbers you give as the answers. Unsupported guesses are worthless. Text of the questions.

Homework # 2, due Tuesday, September 29, 2009, 1:30 PM, on paper, in class. Text of the questions.

Homework # 3, due Tuesday, October 27, 2009, 1:30 PM, on paper, in class. Text of the questions.

Homework # 4, due Tuesday, November 10, 2009, 1:30 PM, on paper, in class. Text of the questions.

Homework # 5, due Tuesday, December 1, 2009, 1:30 PM, on paper, in class. Text of the questions.

Solution to homework and a summary of your grades on the midterm. (Works only from domain .purdue.edu .)

Project 1, due Thursday, September 17, 2009, 1:30 PM, on paper, in class.

Project 2, due Thursday, October 1, 2009, 1:30 PM, on paper, in class.

Project 3, due Thursday, October 29, 2009, 1:30 PM, on paper, in class.

Project 4, due Thursday, November 12, 2009, 1:30 PM, on paper, in class.

Project 5, due Tuesday, November 24, 2009, 1:30 PM, via turnin command.

Mid-Term Exam, Thursday, October 22, 2009, 1:30 - 2:45 PM, in Room LWSN B151. (NOTE DIFFERENT ROOM FOR EXAM!) Do not bring cell phones, laptop computers, or any other device that communicates to the exam.

Final Exam, Wednesday, December 16, 2009, 3:20-5:20 PM, Room HAAS G066. Do not bring cell phones, laptop computers, or any other device that communicates to the exam.

The rest of this page is old and will be changed.

Rijndael, the new AES.

Caesar cipher, CRT.

Large primes via Pocklington-Lehmer.

Euler's Criterion, Legendre symbol.

Quadratic congruences, Oblivious transfer, Zero-knowledge proofs.

Hash and other one-way functions.

MD5 and SHA.

The Birthday paradox.

Threshold schemes.

More about threshold schemes.

Digital Signature Standard.

Subliminal channels; the one in DSA.

Electronic voting.

Elliptic curves.

Some old slides you might enjoy.

Information theory: Definition of entropy.

Information theory: Rate, perfect secrecy.

Key equivocation, unicity distance.

Synchronous and self-synchronous stream ciphers, CBC.

Congruences: CSR, XEuclid, multiplicative inverses.

IDEA.

Entropy question and proposed solution.

Alice and Bob

Random number generation.

(This page last modified November 19, 2009)