"Concurrent Zero-Knowledge" is a technical book that explores the fascinating and useful concepts of zero-knowledge proofs. These proofs are characterized by their seemingly contradictory definition: they are convincing but reveal nothing about the validity of the statement being proved. The applications in cryptography are diverse, as they serve to force malicious parties to adhere to a specified protocol. Furthermore, zero-knowledge proofs provide a valuable foundation for investigating various issues related to cryptographic protocols, such as the secure composition of protocols. A central theme in this context is the question of how to maintain the security of the zero-knowledge property when multiple instances are executed concurrently, particularly in a purely asynchronous model. This issue has both practical and theoretical significance, especially in an era of extensive internet communication. The book offers insights into the theoretical foundations and the development of techniques to address the challenges that arise in this field.