The Mbed cryptography library is a reference implementation of the cryptography interface of the Arm Platform Security Architecture (PSA). This is a preview release of Mbed Crypto, provided for evaluation purposes only.
Mbed Crypto is distributed under the Apache License, version 2.0. See the [LICENSE](LICENSE) file for the full text of the license.
## PSA cryptography API
Arm's Platform Security Architecture (PSA) is a holistic set of threat models, security analyses, hardware and firmware architecture specifications, and an open source firmware reference implementation. PSA provides a recipe, based on industry best practice, that allows security to be consistently designed in, at both a hardware and firmware level.
The PSA cryptography API provides access to a set of cryptographic primitives. It has a dual purpose. First, it can be used in a PSA-compliant platform to build services, such as secure boot, secure storage and secure communication. Second, it can also be used independently of other PSA components on any platform.
* The API distinguishes caller memory from internal memory, which allows the library to be implemented in an isolated space for additional security. Library calls can be implemented as direct function calls if isolation is not desired, and as remote procedure calls if isolation is desired.
* The structure of internal data is hidden to the application, which allows substituting alternative implementations at build time or run time, for example, in order to take advantage of hardware accelerators.
* All access to the keys happens through handles, which allows support for external cryptoprocessors that is transparent to applications.
Since the Mbed Crypto library is a reference implementation of the PSA cryptography API, the library's API documentation is the PSA cryptography API specification. The PSA cryptography API specification consists of the following documents:
* The [PSA Cryptography API overview](docs/PSA_Crypto_API_Overview.pdf).
* The [PSA Cryptography API detailed function reference](docs/PSA_Crypto_API_Reference.pdf), which you can also browse in [HTML format](docs/html/modules.html).
## Compiling
You need the following tools to build the library with the provided makefiles:
* GNU Make.
* A C toolchain (compiler, linker, archiver).
* Python 2 or Python 3 (either will work) to generate the test code.
If you have a C compiler, such as GCC or Clang, just run `make` in the top-level directory to build the library, a set of unit tests and some sample programs.
To select a different compiler, set the `CC` variable to the name or path of the compiler and linker (default: `cc`), and set `AR` to a compatible archiver (default: `ar`). For example:
The provided makefiles pass options to the compiler that assume a GCC-like command-line syntax. To use a different compiler, you may need to pass different values for `CFLAGS`, `WARNINGS_CFLAGS` and `LDFLAGS`.
To run the unit tests on the host machine, run `make test` from the top-level directory. If you are cross-compiling, copy the test executable from the `tests` directory to the target machine.
The `programs/` subdirectory contains sample programs that use the library. Please note that the goal of these sample programs is to demonstrate specific features of the library, and the code may need to be adapted to build a real-world application.
* A driver programming interface, which makes it possible to use hardware accelerators instead of the default software implementation for chosen algorithms.
* Support for external keys to be stored and manipulated exclusively in a separate cryptoprocessor.
Arm welcomes feedback on the design of the API. If you think something could be improved, please open an issue on our Github repository. Alternatively, if you prefer to provide your feedback privately, please email us at [`mbed-crypto@arm.com`](mailto:mbed-crypto@arm.com). All feedback received by email is treated confidentially.
