I don't think you are going to be successful finding out exactly how they work - if it were public knowledge then it would not be too secure, would it?
Steve,
Respectfully, I disagree with that line of reasoning. What you've described is called "security through obscurity", a thoroughly discredited approach that makes the security device user quite vulnerable due to his/her false sense of well security.
I'll jump in here as well. My area of expertise is information security. I specialize in incident response and post-response forensics, but have significant cryptographic experience as well. In the crypto world, "secret" algorithms are treated with about as much credibility as a replacement cipher ( A=1, B=2,C=3, ... ). "Security through obscurity" has no place in any realm of security whether it be physical or logical. If the entirety of your system's (program, computer, house security panel, xyz widget) security is dependent on keeping its inner workings secret, then you have lost before you began.
The perfect example of why hiding *design* details (as opposed to implementation) will eventually lead to a "crack" is the Digital Enhanced Cordless Telecommunications (DECT) standard. This is essentially the "spread spectrum", pseudo-encrypted stuff that just about every cordless telephone in every house in America uses. Many details of the standard are public knowledge, EXCEPT the cryptographic algorithms. It was thought by the industry as a whole that intercepting these communications was beyond the ability of the common hacker (tinkerer) or cracker (tinkerer with criminal intent). This assumption was proven wrong as the hackers found fairly cheap, commodity components to attach to a PC.
Reference Link: <A HREF=http://events.ccc.de/congress/2008/Fahrplan/events/2937.en.html>DECT hack</A>
BTW, that DECT standard is also used for many wireless point of sale systems. Keep that in mind the next time you swipe a credit card at a temporary cash register in department store! It could be purely IP-based wireless using something like WPA2, or if it is older, still using DECT.
Computer and electronic technology is evolving too fast to allow designers the luxury to assume that a capability will remain out of reach of adversaries for the effective lifetime of the product they are designing -- that is the bar you should strive for: Design a system to resist attack for the entirety of its anticipated effective lifetime regardless of current perceived capabilities of would-be adversaries, that is also consistent with with the degree of protection sought and for the value of what is being protected. That very last part is important. It's often OK to say that the protection provided is "good enough," but darn it, *I* want to be able to decide for myself if it is good enough for my needs.
I can't make that informed decision if the basic design is hidden from me.
-Chris