👨‍💻 ezCipher 👾

A simple CLI in C to encrypt and decrypt text using a variety of cipher algorithms.

📜 Description

"In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure... ciphers generally substitute the same number of characters as are input." ~ Wikipedia.

The "Why" of this project

While going through CS50x 2024's Problem Set 2, an idea clicked in my mind to code a Command-Line Tool that would take a Cipher algorithm, the way the user wishes to use it i.e. to choose between an Encryption/Decryption mode, take some text, process it as per the given requirements, and output the result. Simple enough, right?

And thus, I began working on this project, having in mind a similar objective.

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Prerequisites

To use this program, a basic knowledge of ciphers would be a prerequisite.

Currently it features the below cipher algorithms:

1. Caesar
2. Substitution
3. Vigenère

Click on a cipher name to view its description/explanation.

How to run the program?

Requirements: A C compiler, such as GCC or Clang.

1. Clone this repository
2. Open the terminal, and navigate to the repository ~/ezCipher
3. Run the command clang -o ec src/ec.c src/utils/utils.c src/ciphers/caesar.c src/ciphers/substitution.c src/ciphers/vigenere.c

You can also use gcc instead of clang

4. Run ./ec
5. You'll be prompted with this message

error: incorrect number of arguments given, expected 4 -> 1

USAGE: ./ec <cipher> <encrypt/decrypt_mode> <key>

<cipher>:
        caesar
        substitution
        vigenere

<encrypt/decrypt_mode>:
        encrypt
        decrypt

<key>: in accordance with the opted cipher

.. You can either make use of the instructions given here, or follow along for a small example.

An example

1. Let's test the program by using caesar cipher with a key of value, say 2.
2. Run

./ec caesar encrypt 2
Hello, World!
This is ezCipher.

Note: to end giving input, enter a newline and enter the EOF character (Ctrl + Z on Windows, Ctrl + D on Linux).

3. Output:

Jgnnq, Yqtnf!
Vjku ku gbEkrjgt.

4. Run

./ec caesar decrypt 2
Jgnnq, Yqtnf!
Vjku ku gbEkrjgt.

5. Output:

Hello, World!
This is ezCipher.

Voila! Now you know how to use ezCipher for encrypting and decrypting your texts!

To give some syntax on the program usage:

$ ./ec <cipher_algorithm_option> <encrypt_or_decrypt_mode> <KEY> 
<plaintext_spread_over_multiple_lines>
<EOF>
<processed_text>

Where,

<cipher_algorithm_option>
  caesar
  substitution
  vigenere

<encrypt_or_decrypt_mode>
  encrypt
  decrypt
  
<KEY>
  in accordance with the opted cipher

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🎯 Learnings

This was my first C Project that was spread over more than a single file!

I learnt how to use header files to include content from different files into another. The code was written by me, with a side-quest to keep up with some common coding conventions.

I believe the code is well organised to some point. Let me know what I can do better with the code! (more about this in Contributions)

✏️ On Contributions

This marks the first release of ezCipher.

I'd appreciate help in all forms, from beautifying the README or the code itself, to adding new cipher options! Thanks for your kind attention!