File Encryption Utility

• Download source files - 71 Kb
• Download Executable - 85 Kb

Introduction

After a long search for a simple and secure file encryption utility, that is simple and intuitive to use I've decided to write something of my own.

File Encryption utility is a simple tool for encrypting both text and binary files using the blowfish encryption algorithm.

The utility can create a self extracting encrypted file. For a deep view of how to create a self extracted executable check my other article: Creating Self-Extracted Executable .

Features

File Encryption Utility Has the following features:

• Fast & Quick File Encryption/Decryption.
• Internal File Wiping Utility.
• Creating Self-Extracting Encrypted File.
• Explorer Integration (through Configuration Dialog).
• Command Line Parameters.

Language

The File Encryption utility is writen in native C++ using ATL only for windowing classing.

The usage of ATL is minimal so anyone who is not familiar with the library should be able to understand the code as well.

Overview

File Encryption Utility is divided to few small projects:

• FileEnc – The UI of the file encryption utility, also containing the Processing class which is also used by SelfExtract and it is responsible for reading/writing files.
• Enc_Blowfish – Blowfish encryption implementation (based upon Bruce Schneier and Jim Conger implementation).
• SelfExtract – Self Extracting executable "header".
• GenLib – Small Library holding all commonly used items in other project parts.
• Builder – Small Console utility for creating the final File Encryption Executable.

GenLib – The General Library

In order to save time and to have a central point for all general purpose classes I'm working with a static library called GenLib.

A stripped version of the GenLib is available with the File Encryption Utility. In this version you can see the following general purpose classes:

• GenFiles – Openning OpenFile/SaveFile and OpenDirectory Dialog Boxes.
• SelfExtract – Creating Self-Extracting Executable.
• Thread – Implementation of a parent class for classes who want to execute code in separate thread (more information can be seen in the header – thread.h).
• FileWipe – Wiping a File from Hard Drive.

All those classes are under the GenLib namespace.

Additional Encryptions

Inside the FileEnc project there's an interface called EncryptionInterface – implementing this interface can allow you to easily change the encryption the utility uses.

Implementing this interface requires only stream cipher implementation and saves all the overhead of working with files.

Blowfish implementation is statically linked to the utility in order to avoid hacking by changing the dll. With a few minutes of work the utility can support a number of encryption dlls that can be loaded at runtime based on the users decision.

Security

In order to make the utility the most secure I can I've tried wiping information from memory when the application closes.

When looking at the source, you can see that I've used ZeroMemory API and few others APIs to delete information from memory (like the password used).

When encrypting a file you can mark the 'Wipe Source After Process' checkbox and by that insure that the file you're encrypting is not accessible.

Remarks

Decryption does NOT verify password correctness (information is being encrypted without adding any information about the file). As a result when decrypting with the wrong password you will receive a file with junk inside - this is not a bug.

The file encryption is based upon the password length - larger passwords equal better security.

Although I believe that the file wiping method is very secure, to be 100% sure you should use a product dedicated to that purpose.

Reference

Blowfish encryption algorithm - http://www.schneier.com/paper-blowfish-fse.html

Revision History

23 Sep 2002 - Initial Revision

This article, along with any associated source code and files, is licensed under The GNU General Public License (GPLv3)