Reference no: EM133674990

Data Security

Summary: For this task, you will break the four ciphertexts provided in the text files c1, c2, c3, and c4. Each ciphertext was encrypted with a classical method, and they are of differing difficulties to break.

Task description: Included with this assignment on Canvas, are four independent ciphertexts in text files: c1, c2, c3, and c4. You are to decrypt these ciphertexts by finding the unknown keys using analysis techniques learnt during this course. Each ciphertext is one of the following types: transposition, monoalphabetic substitution, or polyalphabetic substitution.

Additionally, you should provide a detailed description of the steps you followed, and the assumptions you made to break the ciphers. In these descriptions, make sure to state what each measurement or action indicates (e.g., IC indicates a period of around 3, single letter frequency distribution indicates a transposition cipher, etc.), also state the motivation behind using the various measurements (e.g., we think that the cipher is polyalphabetic, so we use Kasiski's test).

Afterwards, you will write a brief 300-500-word reflection of your work for this assignment. This should cover how you have used external resources, such as websites, textbooks, large language models, etc., throughout your work. You should also discuss what inspired your problem-solving approaches (e.g. workshop exercises, lectures, web resources, etc.), and any difficulties encountered while problem solving.

Getting started: You will likely want to use a program to help you break the ciphers, i.e., to perform statistical analysis of the ciphertext as well as to decrypt the ciphertext with a chosen cipher and key. We recommend jkrypto whose current version was written by Lawrie Brown and based on the original code by Daryl

Bossert, both at ADFA, Canberra Australia. This program has been used to encrypt all four assignment files.

You may also use another program or write your own. In the former case, clearly cite and link the program(s) you used. In the latter case, either provide a link to the source code repository (on GitHub, GitLab, Codeberg, etc.), or include the source code in an appendix in the submission document. Note that usage of a program that performs a brute force search for the cipher keys, in place of the analysis techniques covered in this course, will incur a penalty of minimum non- zero (if correct) marks for those ciphertext.

As you are working on breaking the ciphers, make sure to note what you have done and the reasoning. These notes could then be refined into your submission document, described in the following section.

For this submission, we expect you to provide a text document in pdf format (i.e., word document, LaTeX document, etc.). In this document, you will include a section for each of the four ciphertext, where each section states the type of cipher, the key, the detailed description of steps followed to find it, and formatted plaintext (letters are correctly grouped together, and grammar rules such as correct capitalisation are added). After your sections on each ciphertext, you will include your 300-500-word reflection. Then, you will conclude this document with a bibliography including external resources and software (e.g., programming languages, Large Language Models, cryptography software, etc.) that you used. Your bibliography should either the IEEE, APA, or Harvard citation standard. You may also optionally include an appendix, which contains extra information that could be helpful for explaining how you made certain observations, etc.

Alongside your submission, you should submit a document stating how each group member contributed to each part of the assignment. This document should be concluded with signatures from each group member. A template of this document is available on Canvas on the Assignment 1 page.