http://www.blackboxvoting.org/ and
http://www.blackboxvoting.com/Two different groups of folks run the two sites. But they will most assuredly be willing to answer and research your question with detailed specifics.
What is needed for these touch screens to work securely are paper **ballots** not just paper records. The programming doesn't even have to be open source if the machine prints out voter readable BALLOTS that can be counted easily by hand (and when you want speed can be counted by a machine that will sift through and read the ballots automatically).
Key points: BALLOTS, not just records. Voter readable! not just machine readable.
According to
This PCWorld article the Sequoia machines use PCMCIA cards to electronicaly store votes on. There is absolutely no possible way for a voter to know that their vote is being stored (and counted) on from that memory card.
The program used to store that information could either be written or infected with a virus to put whatever votes that the hacker wanted onto the card. Just because the *screen* says that your vote went to Bush (or Kerry) doesn't mean that the program increased the vote counter for the correct candidate inside of the (black box, because noone knows what is really going on inside except by studying the effects) software.
Open source is better, but it doesn't solve the problem, either. The *only* way for the public to know for sure that their vote isn't being tampered with is by paper ballots.
I tried to keep things as non-technical as I could. But, it's kinda tough to do on this subject. I'll PM you with this info, also.