For a while now, Debian has been running a project to try to allow anyone to independently confirm that a particular Debian package was indeed built from a particular set of sources, by being able to reproduce the exact build steps themselves. (The security rationale for wanting to do so should be obvious.) As you can imagine, this is seriously non-trivial to achieve, since the least little difference in the version of your compilers or libraries can cause the binaries to differ, maybe not in any important way, but the idea is to end up with no differences at all. The Register has a report on the status of the project here <http://www.theregister.co.uk/2015/02/23/debian_project/>. More background here <https://lists.debian.org/debian-devel-announce/2015/02/msg00007.html>.