Final Project

Lecture: Introduction to Cryptology

Reading: Chapter 1: 1.1, 1.2

Lecture: Substitution Monoalphabetic Ciphers - Caesar, Shift and Affine Ciphers

Reading: Chapter 2: 2.1, 2.2

Programming Lab Assignment

• In this lab you will design a programming implementation for one of the Substitution Monoalphabetic Ciphers.
• You can use C, Java or Python programming languages in the UNIX/LINUX or Windows environment.

  Schedule:

• Start day: Wed, August 29, in class
• Due Day: Wed, Sept 5, in lcass
• The demonstration of the programming solution and the correctness check will be done in class on Wed, Sept 5.
• You would need to send me your source file by e-mail to CSCI391@gmail.com by 4:00 PM, Wed, Sept 5

  Affine Cipher Lab Assessment will consist of two grades

• First grade will be for answering the following questions. Due Day: Wed Sept 5 by e-mail to CSCI391@gmail.com by 4:00 PM

• Second grade will be for programming lab and will consist of the following:

  • Correctness of the programming solution and in class demonstration (90%)
  • Programming style, code appearance, and efficiency of the code (10%)

  Good programming style includes well written comments, indentation, meaningful variable and function names, output expalanation, and more. See links below for more details.

  • The Elements of Programming Style, by Brian W. Kernighan and P. J. Plauger from Wikipedia
  • J. Plauger selected quotes from The Elements of Programming Style
  • Programming Style from Wikipedia
• If you missed the due day class you have to demonstrate the correctness of the program during the course office hours within ONE week of the due day to be qualified for the full credit.
• If you fail to demonstrate the correctness of the program within ONE week of the due day, each late day will result in reduction of the full credit by 25 points.

  For Lab Description see here

Affine Cipher Lab Comments:

• A= 1 is a valid key - Shift Cipher
• B = 0 , B = 25 ARE VALID KEYS!!
• To check validity of the input:
• Valid A: GCD (A, 26)=1
• To find GCD it is better to use Euclidean algorithm:
  1. GCD(a,b) = b, if a%b = 0
  2. GCD(a,b)= GCD(b, a%b), otherwise
• To find mod of negative number (Python does it without special treatment) it is better to use general definition. Some of you just added 26 in case of negative value
• Incorporate functions. Some of you wrote everything in main
• But at the same time, don't exaggerate - I will explain this part in class.
• Confusion between programming structures and data structures.
  • Examples of the programming structures: loops, if-else statements, functions, etc. (INT (integer) - variable type)
  • Data structure is a particular way of storing and organizing data in a computer so that it can be used efficiently. Examples: arrays, linked lists, stacks and queues, trees, etc.

Lecture: Cryptanalysis of Affine Cipher

Cryptanalysis of Affine Cipher Part I
Cryptanalysis of Affine Cipher Part II
Wolfram|Alpha: Computational Knowledge Engine

Affine Cipher Cryptanalysis Graded Lab

• Problem 1: Question 4 page 55 from your textbook

• Problem 2: Question 5 page 55 from your textbook

• Problem 3: The ciphertex

  EUJPE HUNKL NPOJK VNKSJ FKTBO LCHBU PBOMM NPKBK HPBOM BMAHU PNKLN POJKV NKSJF KRJTC JUKPB OMSJE HP

  is the result if an affine cipher encipherment. Hint: Three most frequent letters in the ciphertext correspond to the plaintext letters O, S, and T not necessarily in that order

• Bonus (20 points):Write a program that accepts ciphertext only. Find the keys and decipher the message. Use letter frequency analysis and apply known plaintext attack after making assumption on possible plaintext letters. Use your program to solve Problem 3 from the list.

  Test Inputs for Bonus Program

  • Ciphertext 1: SJEFWLUQGGWJUYQEUDFQJRUORFCAJOUNIHJOFFWJU

  • Ciphertext 2: VFFNJBSDRVYTXFVGJYTVMFSVJGTAIATHVWBYTVYOFVJBSZFJINJBSDJVYETABTWAFARIFAFVVJGV

  • Ciphertext 3: ACCKHUQFCOMPCIQVCMOBFJQVMZYPOLOHOBICFTCOHJTUHQZCMJUHC

• For each problem you have to write detailed solution and explain each step.

• You have to write a program that finds keys using an algorithm that was explained in the lecture. The input for the program is four characters ( two plaintext letters and two ciphertext letters). The output for the program: affine cipher keys A and B.

• You will use the above program to perform calculations.

• Submit source file and detailed solution.

• Due Day: Friday, 14 by the end of the class time

  Important! If you will struggle with the programmin part, this assignment could be done without programming for the maximal grade of 89.

Vigenere Cipher

Web Resources: Sharky's Vigenere Cipher

Vigenere Cipher

Vigenere Cryptanalysis Part I

Vigenere Cryptanalysis Part II

Vigenere Python Program

Vigenere Graded Lab

Computer Ethics Component

• You will work in class on Computer Ethics Component on Monday and Wed this week. There is no class on Friday, October 5.
• You have to choose your implementation and team option by the end of the class on Monday and send me an e-mail indicating your choice.
• Due Day and Presentations Day: Monday, October 8
• Computer Ethics Component Description

Hill Cipher

Hill Cipher

Quiz 2 Preparation and Info

Quiz 2 Prep

Java Applet to find modular multiplicative inverse - written by Andrew Burns

QUIZ 2

HILL CIPHER CRYPTANALYSIS

Example and Theory

In Class Practice

Problem 1: The ciphertext ZWSENIUSPLJVEU was obtained by Hill Cipher using 2x2 matrix. You know that the block ZW corresponds to the plain text HO and the block PL corresponds to the plain text UT. Determine the key matrix and then use it to decipher the rest of the message.

Problem 2:The following plaintext THE GOLD IS BURIED IN ORONO was encrypted by Hill Cipher with 2X2 key matrix and the correspondent ciphertext is GZSCXNVCDJZXEOVCRCLSRC. Find a key matrix.

HILL CIPHER CRYPTANALYSIS PROGRAMMING LAB - Due Day Friday, October 26 by 11 AM - beginning of the class time!

Graded Lab

To test your program use the following quiz questions - you must submit the answers for the quiz questions by the end of the class on Friday, October 26, 11:50 AM

HILL CIPHER CRYPTANALYSIS Quiz