Even with pgp you'd need a whole lot of infrastructure. Where to get the public key from etc. Ubuntu requires pgp keys for their ppa and provides a keyserver. Since a lot of gems seem to use github nowadays, maybe an option to provide a pgp key on github would be great. That would allow to trust at least the most interesting projects - rails, db-layers, rack, etc. which could limit the fallout of an attack against rubygems.org