Hi,
just for the record: http://hackage.haskell.org/package/bindings-nettle is a low level interface; think of it as the *.h header files in C.
I started http://hackage.haskell.org/package/nettle as a "safe" binding; it should ensure that you can't screw up memory allocation and so on, because otherwise I don't see a reason not to use C in the first place :)
regards, Stefan