The Cashu Development Kit (CDK) is designed to be a lightweight, flexible, and secure Software Development Kit (SDK) that allows developers to create Cashu applications without having to implement the Cashu protocol themselves. CDK will be written in Rust to harness the security and performance advantages of the language, as well as to ensure compatibility with a wide range of platforms. Additionally, the library will provide support for multiple programming languages through Foreign Function Interface (FFI) bindings to the native Rust core. CDK would enable mobile wallets and mints to share the same codebase. Mobile wallets could integrate the Rust codebase directly or via FFI bindings, this would enable the development of cross-platform Cashu wallets and mints, without the developer having to build Cashu internals.