Crypto 101 is an introductory book about cryptography authored by lvh, available as an open-source repository on GitHub. The book serves as an educational resource designed to teach fundamental cryptographic concepts to beginners. It provides comprehensive coverage of cryptographic principles, algorithms, and practical applications in an accessible format. The repository contains the complete source code for the book, allowing users to build their own copies locally. The build process requires running 'make book' in the root directory, with Docker recommended due to the extensive dependencies required for compilation. Currently available only in English, the project welcomes community contributions for translations into other languages. The repository includes dedicated dockerfiles for Ubuntu and Fedora systems to facilitate the installation of necessary build dependencies. The book is structured as a learning resource that progresses from basic cryptographic concepts to more advanced topics, making it suitable for students, developers, and security professionals seeking to understand cryptography fundamentals.