Escher helps you creating secure HTTP requests (for APIs) by signing HTTP(s) requests. It's both a server side and client side implementation. The status is work in progress.
The algorithm is based on Amazon's AWS Signature Version 4, but we have generalized and extended it.
More details are available at our Escher documentation site.
The Test Cases are included as git submodule.
Don't forget to use the git pull --recurse-submodules and the git clone --recurse-submodules to pull and clone the remote repository.