This book is a walk through the Wasefire project.


Provide a simple-to-use and secure-by-default ecosystem for firmware development.


The ecosystem aspires to be accessible to projects and developers regardless of their familiarity with developing secure firmware:

  • No embedded expertise required: Regular software engineers can develop firmware.
  • No security expertise required: The ecosystem provides secure-by-default options.
  • No enforced programming language: Developers may use the language of their choice, as long as it compiles to WebAssembly or the target architecture.
  • No enforced development environment or build system: Developers may use their usual setup.


Security is the responsibility of the ecosystem, not the developer. The following security mechanisms are (or are planned to be) in place:

  • Sandboxing of the firmware functions (called applets) from each other and from the firmware runtime (called platform).
  • Secure implementation within the platform boundaries (e.g. side-channel resistance, fault injection protection, etc).
  • Security reviews for the supported boards (e.g. side-channel attacks, fault injection, etc).
  • User documentation when the security must rely on user behavior, for example when a configuration is insecure.

Even though the default is to be secure, the ecosystem will provide options to opt-out from some of the security features for performance or footprint reasons. In other words, the developer is able to choose the trade-off between security and performance, defaulting to security without explicit action.


Being both simple-to-use and secure-by-default actually goes hand in hand. It cannot be expected for humans to never do mistake, even if they have embedded and security expertise.

  • By being simple to use, developers will prefer using the ecosystem solution rather than implementing their own, thus using a secure-by-default solution rather than a possibly insecure implementation.
  • By not being concerned with security and embedded details, developers can be more productive and focus on the actual firmware behavior, following the well-lit path for all security and embedded questions.


The project is not trying to build a self-service applet store. In particular, users are developers. A self-service applet store may come at a later phase or may be done independently by another project. The project will provide anything needed for such applet store to be secure and easy to use.


The project is still work in progress and many components might change in the future. However, the project follows the usual Rust semantic versioning to avoid unexpected breakages.