Applied Cryptography is a book published by Electronic Industry Press 20 1 1. This book can be used as a textbook for senior undergraduates and postgraduates majoring in cryptography, applied mathematics, information security, communication engineering, computer, information management, e-commerce, Internet of Things, networked measurement and control, etc. It can also be used as a reference for researchers and engineers engaged in the application, design and development of network and communication information security related fields. Especially suitable for beginners who find it difficult to learn cryptography. This book introduces the basic concepts, basic theories and typical practical technologies of applied cryptography. The content involves cryptography foundation, classical cryptography, introduction to cryptography mathematics, symmetric cryptography, asymmetric cryptography, hash function and message authentication, digital signature, key management, stream cryptography and new progress in cryptography. The book also introduces the application methods and technologies of cryptography in digital communication security, industrial network control security, wireless sensor network sensing security, radio frequency identification security, e-commerce payment security and other typical fields. The outstanding feature is to analyze the principle of complex cryptographic algorithms in simple terms and emphasize the engineering application skills of modern cryptography, so that readers can get started in a little time and master the essence of applied cryptography as soon as possible.