This is a minimal reimplementation of libmacaroons (https://github.com/rescrv/libmacaroons) in OCaml.
It consists of two findlib libraries:
first provides a functor over the required cryptographic operations, while the
second uses libsodium for crypto, and is only installed if the OPAM package
sodium is installed.
See the paper http://research.google.com/pubs/pub41892.html to learn about Macaroons.