krypt

A file encryptor written in pure x86-64 Assembly for Linux.

Overview

krypt is a minimalist, modular tool that performs in-place XOR encryption/decryption. It bypasses libc and communicates directly with the Linux kernel via syscalls.

Architecture

The project is split into three distinct modules to maintain separation of concerns:

• src/data.asm: The transformation engine. Implements a stateful, circular XOR cipher.
• src/io.asm: The interface layer. Handles raw Linux syscalls (sys_open, sys_read, sys_write, sys_lseek).
• src/main.asm: The orchestrator. Manages the execution flow and state persistence across data chunks.

Engineering Highlights

• Zero Dependencies: Does not link against libc.
• In-Place Transformation: Uses sys_lseek to overwrite bytes directly on the disk, minimizing memory footprint and I/O overhead.
• Stateful Chunking: Processes files in 1KB chunks while maintaining the encryption key's offset, allowing it to handle files of any size.
• Modular Design: Uses the System V AMD64 ABI for internal function calls, making it easy to swap the encryption logic.

Build Requirements

• NASM (Netwide Assembler)
• GNU Linker (ld)
• GNU Make

Usage

1. Clone the repo:

   git clone [https://github.com/your-username/krypt.git](https://github.com/your-username/krypt.git)
   cd krypt
   
   

Build the binary:

  make 

Run

./bin/krypt