To better understand "THE MASTER KEY" to stealing elections with computers, watch: 
Fraction Magic - Detailed Vote Rigging Demonstration ( 24:40 )
Bev Harris
Published on Oct 31, 2016
I'LL NEVER TRUST ANOTHER COMPUTER COUNTED ELECTION AGAIN !
Things have changed!
Bennie Smith, a Memphis computer programmer, discovered HOW this is done through a- " ... a GEMS tabulator—for Global Election Management System—which is a personal computer installed with Diebold software that sits in a windowless room in the county’s election headquarters.
The tabulator is the brains of the system.
It monitors the voting machines, sorts out which machines have delivered data and which haven’t, and tallies the results.
As voting machines check in and their votes are included in the official count, each machine’s status turns green on the GEMS master panel.
A red light means the upload has failed.
At the end of Memphis’s election night in October 2015, there was no indication from the technician running Shelby County’s GEMS tabulator that any voting machine hadn’t checked in or that any votes had gone missing, according to election commission e-mails obtained by Bloomberg Businessweek.
Yet as county technicians followed up on the evidence from Smith’s poll-tape photo, they discovered more votes that never made it into the election night count, all from precincts with large concentrations of black voters. ... "
Bloomberg's article titled How to Protect Against Election Day Hacking gives more proof of this by Memphis computer programmer Bennie Smith.
- "... The method Smith used to catch the problem should be a playbook for any candidate, party or concerned citizen worried about the accurate tallying of their votes:
- Smith snapped some pictures of printed voting tallies (known as poll tapes) at a high-turnout polling location and then compared the results there to the electronic tabulations.
Smith has created a proof-of-concept program called Fraction Magic, showing how corrupt officials could tamper with GEMS to manipulate election outcomes.
This map shows all the locations across the U.S. that use the GEMS vote-tabulation system as of Nov 2016.