I might also add that two of my favorite security programs, Password Safe and TrueCrypt, are open source. I wouldn't trade them for anything.
At first glance, this seems counter-intuitive. If any hacker can read your code, why can't they use that knowledge against you? Think of what the Rebel Alliance did with the Death Star plans in the original Star Wars.
Reality and Star Wars don't always coincide. When everyone has access to the source code, a great many experts are able to examine that code thoroughly and determine if it really is secure. That's prohibitively expensive if the only people with access to the code are on the payroll.
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