ipcrypt was designed by Jean-Philippe Aumasson to encrypt IPv4
addresses with 16-byte keys, where the result is still an IPv4 address.
Derived from the implementation at: https://github.com/veorq/ipcrypt
The documentation for master is located at https://stbuehler.github.io/rustdocs/ipcrypt/ipcrypt/; released versions are documented at https://docs.rs/ipcrypt.