Keyczar is a cryptographic toolkit that supports encryption and authentication for both symmetric and public-key algorithms. It addresses some of the issues by choosing safe defaults, tagging outputs with key version information, and providing a simple application programming interface. The toolkit’s key versioning system makes it easy to rotate and revoke keys, without worrying about backward compatibility or making any changes to source code. We look forward to working with the open source community and continuing to make cryptography safer and easier to use.”]
Source: https://security.googleblog.com/2008/08/keyczar-safe-and-simple-cryptography.html