practice.md

Practice Problems

Here are some selected problems for practice. There are approximately 1-3 different problems per subject covered, excluding additional information. They are intended to be used not only as practice, but also as a means to further teach yourself some of the intricacies of what was covered. Solutions are available here, along with written explanations and steps. If you would like to reach out to me regarding these problems, please find my contact information on my profile. Good luck, and have fun!

Table of Contents

• Shift Ciphers
• Viginère Ciphers
• Feistel Networks
• RSA
• ElGamal
• Elliptic Curves

Shift Ciphers

Question 1:

There is a shift cipher known as ROT13. ROT13 can be defined as taking an input in the form of a string, converting it to the numerical representation as described by the mapping in the readme, and adding 13 to it modulo 26.

Part A:

Show that $E_{K}$ and $D_{K}$ are the same. Why is this? Demonstrate it for the general case.

Part B:

Find the key (number of shifts) utilized in the ciphertext here: Svyfcu pfli jfclkzfe.

Viginère Ciphers

Feistel Networks

RSA

ElGamal

Elliptic Curves