Hello. My name is Sang-Yoon Chang and I'm an Assistant Professor at the Computer Science Department at UCCS University of Colorado, Colorado Springs. I received my PhD from the Electrical and Computer Engineering Department at UIUC University of Illinois at Urbana-Champaign. In graduate school, I worked on securing the wireless link for computer networks. And my work involve theoretical analysis and design, as well as the use of software-defined radios and microcontrollers for implementation and validation. Since my PhD, I continued my research to secure networking systems and my research interests span across multiple disciplines such as computer security, applied cryptography, computer network and wireless communications. My research also has high synergy with the recent developments in IoT, Internet of Things, and cyber physical systems. This specialization focus on applied cryptography, which provides fundamental set of techniques for securing information transfer, whether that information transfer is in the forms of networking transmission or data access of a file. While cryptography originated from protecting the secrecy or the confidentiality of messages, its application nowadays also includes integrity protection, such as, digital transactions and bitcoins, and key establishment, which can also help with the system availability. For example, by providing a seed or a key for random access. In addition to learning the cryptographic techniques and their purposes, so that you can identify and apply the techniques, in this specialization, you will also learn about the history and the progression of cryptography with concrete examples. We will discuss about the relevant questions raised during the cryptographic developments. Those questions that are significant enough to affect the algorithm developments and the cryptography landscape. The motivation for taking such approach is, so that this specialization can provide you with a better feel about the logic behind the cryptographic scheme design. In other words, while applying or using a cryptographic algorithm may be possible while treating the algorithm as a black box, and only knowing the input-output relationships, in this specialization, you will also have the opportunity to practice the logic of the cryptographic design and get a better sense of what is happening within the black box, and how and why it is designed that way. Furthermore, you will be able to analyze the security strength and properties of cryptographic schemes. For example, if somebody presents you an algorithm that is overly complex, then you can follow the logic and evaluate the algorithm to judge whether the added complexity provides any value to the system. This actually happened to me when one of my PhD students wanted to build its own cryptographic algorithm, with the impression that greater complexity is sufficient for improved security. In another case, I was in a meeting with people working as System Integrators of government-owned critical infrastructure and they claimed that their system is so complex, that it is impossible for the attacker to learn and attack the system. In contrast to what it may seem like, cryptography research and development is often driven by simplicity, transparency and efficiency. For example, advanced mathematics are used for simpler descriptions of the cryptographic algorithms. The algorithm designs are public, and the implementations are efficient for computer processing, and as easy if the key is known. I'm really excited to launch this mook, and I hope you find it intriguing and helpful. Welcome to Applied Cryptography.