This project is a common crypto abstraction that can be shared by software projects related to card payment processing. The intention is to ease porting to different software cryptographic implementations (like MbedTLS or OpenSSL) or porting to hardware cryptographic implementations (as found on secure microcontrollers). The intention is also to expose simple abstractions that are relevant to card payment processing, instead of providing for all imaginable use cases.

Note that this is not intended to be a standalone project. It is intended to be a collection of object libraries that can be added to other projects as a submodule. The object libraries have hidden symbol visibility such that they are not exposed as part of the API of other projects.

• C11 compiler such as GCC or Clang
• CMake
• At least one supported cryptographic implementation (see below)

Supported cryptographic implementations:

• MbedTLS
• OpenSSL

This CMake project can be added to CMake parent projects using the CMake add_subdirectory() command. When this project is added to a parent project, the test subdirectory is not added automatically. Parent projects can add the test subdirectory manually if the tests are of interest to the parent project. However, note that the test subdirectory requires the CMake CTest module and that the tests will only be built when the BUILD_TESTING option is enabled (CTest enables it by default).

An example of adding this project to a parent project would be:

add_subdirectory(crypto)
add_subdirectory(crypto/test)

Note that it is not necessary, and not recommended, for EXCLUDE_FROM_ALL to be specified when adding this project to a parent project. This project already specifies EXCLUDE_FROM_ALL for each add_library().

This project provides several variables to the CMake parent scope for the parent project to use:

• CRYPTO_PACKAGE_DEPENDENCIES for the parameters of find_dependency() when generating the parent project's CMake package configuration file
• CRYPTO_PKGCONFIG_REQ_PRIV for the dependencies in the Requires.private field when generating the parent project's pkg-config file
• CRYPTO_PKGCONFIG_LIBS_PRIV for the linker flags in the Libs.private field when generating the parent project's pkg-config file

If MbedTLS is not available, the FETCH_MBEDTLS option can be specified to download and build a local copy during the CMake build. If the platform provides MbedTLS but it should not be used, the CMAKE_DISABLE_FIND_PACKAGE_MbedTLS option can be used to prevent CMake from finding it. This option can even be used without FETCH_MBEDTLS to ensure that CMake finds and uses a cryptographic implementation other than MbedTLS.

When specifying FETCH_MBEDTLS together with BUILD_SHARED_LIBS, it may also be necessary to use USE_SHARED_MBEDTLS_LIBRARY to ensure that MbedTLS is built as a shared library.

Copyright 2021-2024 Leon Lynch.

This project is licensed under the terms of the MIT license. See LICENSE file.