Integrity checking for cabal

Hello, I'm pretty new to Haskell and I hope this list is the appropriate place to ask the following question: When I use cabal to install a libary or a program, are there any integrity checks done? Preferably, are there digital signatures checked? So far I couldn't find anything related to integrity checking in cabal -- but I found it a bit hard to believe that there is no such mechanism at all. If there is none, are there any plans on adding such a mechanism? For instance, one could configure cabal to complain whenever a package's signature could not be checked and implement some light-weigth signature checking via pgp-keys. Thanks, m.