Crypto library is blocking

[jt-turner-upkeep]

This library uses the crypto library that are blocking calls. So not a great idea to use for node.js services. Any chance you are thinking about moving this to a async methods?

Something like: https://github.com/ronomon/crypto-async

[gkwang]

I'll put in in the backlog, but no timeline of when it'll be implemented.
We welcome any contributions if you would like to help.