I have been working on Nettle bindings for Swift (Apple's somewhat new language, which is starting to become useful on non-Apple platforms). The bindings are incomplete and I'm still figuring out what the most ergonomic API is, but the package can currently be found here:

https://github.com/wiml/swift-nettle

It should be usable with SwiftPM and Swift 5.0.1 or 5.1.

Feedback and contributions are very welcome. I wrote this to solve a specific problem, and so the parts of Nettle that I didn't need are either missing or might not be easy to use. (In particular, I didn't need symmetric encryption, which is a pretty large missing piece!)

Wim Lewis / wiml@hhhh.org