File Encryptor is a command-line program written in x86 Assembly (ASM) that encrypts or decrypts any file using a given password. This project was created as part of the 2024 RowdyHacks Hackathon and significantly expanded my understanding of assembly language.

• Encrypt/Decrypt Any File: Uses XOR encryption with a custom, rotating key to secure any file.
• Command-Line Based: Lightweight and efficient for command-line environments.
• Educational Journey: A deeper dive into Assembly for low-level programming enthusiasts!

• NASM: Ensure that the Netwide Assembler (NASM) is installed on your system.

1. Clone this repository:

   git clone <repo_url>

2. Run the make command to compile the program:

   make

3. Place the file you want to encrypt in the same directory as the program.

To encrypt or decrypt a file, run:

./file-encryptor <mode> <file_path> <password>

• mode: Specify encrypt or decrypt.
• file_path: Path to the file you want to secure.
• password: The encryption key, which can be any string.

I took on this project with only limited knowledge of assembly, having briefly encountered inline assembly in a Computer Organization class. This hackathon gave me a chance to dive into ASM in-depth and work through challenges on the fly.

1. Assembler Choice: I chose NASM for its rich documentation and ease of use in assembly projects.
2. Hello World: Started by learning the basics with a "Hello World" program to get comfortable with assembly, compilation, and linking.
3. Makefile: Created a Makefile to streamline compiling.
4. Sections: Learned about different sections like .text and .data to manage code and data.
5. Command Line Arguments: Gained experience with the cdecl calling convention and handling command-line arguments.
6. Encrypt/Decrypt Mode: Implemented XOR encryption, realizing later that XOR is symmetric—encryption and decryption work identically.
7. Encryption Function: Wrote the main encryption/decryption logic, using system calls to handle file operations in ASM.
8. Rotating Key: Started with a single-byte key and then expanded it to support a rotating key for more robust encryption.
9. GDB: I learned a lot about how useful gdb can be and started to get comfortable using it.

This project was both challenging and rewarding. I faced moments of doubt but ultimately came away with a much deeper understanding of low-level programming and assembly language, and I'm not even scratching the surface!

• Improve variable management to streamline the code further.
• Add a custom file extension for encrypted files to distinguish them more easily.

Thank you to the organizers of RowdyHacks 2024, UTSA and the ASM community for the resources and support throughout this project!