A Brief Look at the Principle Behind Packed Programs

Tue, 07 Jul 2009 20:29:10 +0000

Most people have heard of packers, such as UPX, but do you know how they work? Have you ever tried writing one? Is it hard? Actually, the principle is quite simple. Let me, Feng-lai, explain it for you~

The first step in writing a packer is to get the binary file of the program you want to pack. Everyone knows that every file on a computer is a binary file, right? A binary file is made up entirely of 0s and 1s. So what do you do with it once you have it? Encrypt it, of course. The simplest encryption method would be to invert every bit: each 0 becomes a 1 and each 1 becomes a 0. But you can’t just run the encrypted file directly, so the second part comes next.

HxD - An Excellent Hex Viewer

Sun, 28 Jun 2009 09:00:10 +0000

Today I am introducing a program called HxD. It lets you view a file’s hexadecimal bytes. Although HxD is free, it is no less capable than professional-grade editors. HxD not only supports basic hex viewing but can also directly control memory. HxD also has an export feature: you can export modified files directly as source files for languages such as VB or C++. Personally, I think anyone who often works with computers should keep it on a USB drive, just in case.

Reverse Engineering on Lin's Blog

A Brief Look at the Principle Behind Packed Programs

HxD - An Excellent Hex Viewer