Multi-Layer File Obfuscator (C#)

A console utility demonstrating a multi-pass substitution cipher for text files. This program applies a simple, keyed character-shifting mechanism across multiple layers, requiring the successful reversal of each layer for decryption.

Disclaimer: This tool is for educational demonstration of cipher chaining and key management concepts. It uses a basic Vigenère-like cipher and is not suitable for protecting sensitive or mission-critical data.

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Features & Mechanism

Core Logic

The application uses the Unicode/ASCII value of each character in the file content and shifts it by the corresponding value of a character in the key (password), cycling through the key length.

The fundamental operation is a character code addition/subtraction, handled with modulo arithmetic to manage wrap-around within the 16-bit character space ($0x10000$): $$ \text{Transformed Char} = \begin{cases} (c + \text{pwdChar}) \pmod{0x10000} & \text{for Encrypt} \ (c - \text{pwdChar}) \pmod{0x10000} & \text{for Decrypt} \end{cases} $$

Multi-Layer Chaining

• Encryption: Passwords are applied sequentially (Layer 1 $\to$ Layer 2 $\to$ ...).
• Decryption: Passwords must be applied in reverse order (Layer $N \to$ Layer $N-1 \to$ ...), reversing the shift for each layer.

Key Structure

The program enforces a single Master Password format, which contains all necessary keys and the layer count for successful decryption:

layers|password_1|password_2|...|password_N

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Quick Start

Prerequisites

• .NET SDK (any modern version, e.g., .NET 8).

Usage

1. Compile: Build the project using the .NET CLI.

   dotnet build

2. Run: Execute the compiled application (path may vary based on your project structure).

   .\bin\Debug\net8.0\Program.exe

Example Flow (Encryption)

1. Select Mode: Choose Encrypt (en).
2. Configuration: Specify the file path and the number of layers (1-10).
3. Key Generation: Enter the First Password (or type gen-pwd). The application auto-generates keys for subsequent layers.
4. Master Password Output: Upon completion, the console displays the crucial Master Password. Securely save this string; it is the only way to restore your file.

Encrypt (en) or Decrypt (de)? en
...
Layers (1-10): 3
...
MASTER PASSWORD (SAVE THIS!): 3|MyCustomKey|&d4fP!xZ9kL2|Jm-aH+*rQp(7