(This book takes encryption and decryption as the starting point, and describes many basic knowledge and technologies in the field of software security, such as debugging technology, reverse analysis, encryption maintenance, shell development, virtual machine design, etc. When the reader masters the content of this book, it is very easy to expand in the fields of vulnerability analysis, security programming, virus analysis, software maintenance, etc. These knowledge points are all connected to each other. Domestic colleges and universities have not paid enough attention to the teaching of software security, and many aspects are still blank. In recent years, many enterprises have an increasing demand for software security technical talents. From a work point of view, mastering this technology can improve one's own competitiveness; from a personal growth point of view, researching software security technology helps to master some underlying knowledge of the system, and is an important way to improve industry technology. As a qualified programmer, in addition to mastering requirements analysis, design patterns, etc., if you can master some basic knowledge of the system and be familiar with the underlying structure of the comprehensive system, you will benefit a lot from your work. This book can be used as a software safety aid teaching material for campus or training organizations. It is a rare and rare book for safety technology enthusiasts, debugging personnel, and program development personnel.)