Keyczar is a cryptographic toolkit designed to make it easier and safer for developers to use cryptography in their applications. It supports authentication and encryption with both symmetric and asymmetric keys. Cryptography is easy to get wrong. Developers can choose improper cipher modes, use obsolete algorithms, compose primitives in an unsafe manner, or fail to anticipate the need for key rotation. Keyczar abstracts some of these details by choosing safe defaults, automatically tagging outputs with key version information, and providing a simple programming interface.