If by "google does not provide keywords" you mean that you can't see the keywords users search in order to visit your site, in G analytics and you see [not provided], there is no way to see this keywords even if you want to pay, since g00gl3 now doesn't reveal the searches of sig-in users (and today the majority of internet users use one-or-another G service so they are connected most time...)
I think that latter you will see some keywords, from non-connected users. But as you can imagine the ratio will be 75 to 25.