Book Image

Mastering Reverse Engineering

By : Reginald Wong
Book Image

Mastering Reverse Engineering

By: Reginald Wong

Overview of this book

If you want to analyze software in order to exploit its weaknesses and strengthen its defenses, then you should explore reverse engineering. Reverse Engineering is a hackerfriendly tool used to expose security flaws and questionable privacy practices.In this book, you will learn how to analyse software even without having access to its source code or design documents. You will start off by learning the low-level language used to communicate with the computer and then move on to covering reverse engineering techniques. Next, you will explore analysis techniques using real-world tools such as IDA Pro and x86dbg. As you progress through the chapters, you will walk through use cases encountered in reverse engineering, such as encryption and compression, used to obfuscate code, and how to to identify and overcome anti-debugging and anti-analysis tricks. Lastly, you will learn how to analyse other types of files that contain code. By the end of this book, you will have the confidence to perform reverse engineering.
Table of Contents (20 chapters)
Title Page
Copyright and Credits
Packt Upsell
Contributors
Preface
Index

x86


Like any other programming language, assembly language has its own variables, syntax, operations, and functions. Every line of code is processes a small amount of data. In other words, every byte is read or written per line of code.

 

Registers

In programming, processing data requires variables. You can simply think of registers as variables in assembly language. However, not all registers are treated as plain variables, but rather, each register has a designated purpose. The registers are categorized as being one of the following:

  • General purpose registers
  • Segment registers
  • Flag registers
  • Instruction pointers

In x86 architecture, each general purpose register has its designated purpose and is stored at WORD size, or 16 bits, as follows:

  • Accumulator (AX)
  • Counter (CX)
  • Data (DX)
  • Base (BX)
  • Stack pointer (SP)
  • Base pointer (BP)
  • Source index (SI)
  • Destination index (DI)

For registers AX, BX, CX, and DX, the least and most significant bytes can be accessed by smaller registers. For AX, the lower 8 bits can be...