croc is a secure, peer-to-peer file transfer tool that operates via a relay server for NAT traversal. It uses Password Authenticated Key Exchange (PAKE) for authentication and end-to-end encryption (AES-GCM or ChaCha20-Poly1305) to protect data in transit. The application consists of a Go CLI client, a standalone web server (croc-web), and a React/Vite web frontend that uses WebAssembly to perform crypto operations in the browser. Files are split into chunks, optionally compressed, and transferred over multiple TCP connections with resume support. The tool also supports an asynchronous 'stored transfer' mode where encrypted files are temporarily stored on the relay server and can be downloaded by recipients using access tokens. The codebase is well-structured with a custom CLI framework, modular crypto and compression packages, and a comprehensive test suite covering core transfer logic, security properties, and end-to-end browser tests. The web client includes a blog with deep technical articles about the protocol design.