<p>Glen --</p>
<p>There is a box of 50 or so cut combination locks (still "work", they just can't lock anything) on the hackshelves in a bin. Feel free to use them. :)</p>
<p><blockquote type="cite">On Sep 9, 2012 11:56 AM, "Glen Jarvis" <<a href="mailto:glen@glenjarvis.com">glen@glenjarvis.com</a>> wrote:<br><br><div><div>-----BEGIN PGP SIGNED MESSAGE-----</div><div>Hash: SHA1</div>
<div><br></div><div>I am interested in communicating difficult concepts in very easy ways.</div><div>Something about that gives me a kick. I want to get some physical</div>
<div>lock-key apparati and I thought the lock picking group may help point</div><div>me in the right direction.</div><div><br></div><div>I have been explaining public-key encryption to new users for several</div><div>weeks now. I found the main source of confusion was that they were</div>
<div>using the concept of symmetric keys and having two keys just didn't</div><div>fit that model. </div><div><br></div><div>I found it most helpful use the word 'key' *only* when discussing</div><div>symmetric keys and *never* use it when discussing public key</div>
<div>cryptography. I would substitute the words "safe" and "combination"</div><div>(concept per GNU Privacy Handbook</div><div>(<a href="http://www.gnupg.org/gph/en/manual.html" target="_blank">http://www.gnupg.org/gph/en/manual.html</a>) instead of key for public</div>
<div>key encryption.</div><div><br></div><div>So, we would say "your public safe" each time we were referring to the</div><div>concept of a public key. And, we would say "your private combination"</div>
<div>when we were talking about the private key concept. Because this</div><div>repetitively used the words "public and safe" and "private and</div><div>combination," it seemed to help a *lot*. In fact, when we started</div>
<div>talking about "John's public safe" and "my public safe" and "my</div><div>private combination" it made sense.</div><div><br></div><div>I also used the short story of: "Imagine I'm not home and you're</div>
<div>trying to get me a message that you know ONLY my eyes will see. You</div><div>call me on the phone and discuss but don't want to give me the message</div><div>over the phone. I explain that, outside my house, on my porch, I have</div>
<div>a safe that's bolted down into the concrete -- it can't easily be</div><div>stolen. I leave the safe unlocked. Only I have the combination to it.</div><div>So, why don't you put your message inside the safe (since I'm not</div>
<div>home), spin the tumbler to lock it, and know only I can unlock it when</div><div>I get home."</div><div><br></div><div>This concept worked very well (it seemed to work in all cases thus</div><div>far). It's something physical that people can relate to. Yes, the safe</div>
<div>can be drilled into and the message stolen. and, yes, the concrete</div><div>could be destroyed and the safe stolen. But, those things are pretty</div><div>hard to do and can take a while -- I may be home before they get by</div>
<div>with it. Those same concepts are true for Public Key encryption.</div><div><br></div><div>I want to take this physical concept and make a classroom apparatus</div><div>for it. I want a bunch of small padlocks (the small cheap kind is</div>
<div>fine). But, I need to get like 5 copies of the exact padlock (i.e., I</div><div>want one single key to open many different padlocks). The idea is that</div><div>each padlock represents a public key and they're passed around the</div>
<div>room willy nilly so anyone can have one (I'll probably paint or in</div><div>some way color code them so each set is easily identifiable). And,</div><div>then, if I could get a small box or carton or diary or something that</div>
<div>would lock, we can have people write messages, put them in the box,</div><div>and then lock it with a lock (e.g., I'll use a red lock because Glen</div><div>has the keys for red locks and I can get a message to him). These can</div>
<div>be passed around the room to be delivered to the person in question. I</div><div>have no idea what the box thingy will look like -- I'm open to</div><div>suggestions.</div><div><br></div><div>I'm more troubled where can I buy a set of identical padlocks where</div>
<div>only one key will open them? (e.g., 1 key and 5 padlocks). And, then</div><div>can I buy several sets?</div><div><br></div><div>I thought the lock-picking group may be able to point me to a vendor</div><div>or the right location. I hope not to spend more than $30 or so on</div>
<div>this, so we're talking reasonably cheap small locks if possible. I</div><div>will only use this a few times when teaching a class... (although, I</div><div>think with this apparatus we could easily teach third graders how</div>
<div>public key cryptography works)..</div><div><br></div><div>Any help would be appreciated.</div><div><br></div><div><br></div><div>Warmest Regards,</div><div><br></div><div><br></div><div>Glen Jarvis</div><div>- -- </div>
<div>"Pursue, keep up with, circle round and round your life as a dog does</div><div>his master's chase. Do what you love. Know your own bone; gnaw at it,</div><div>bury it, unearth it, and gnaw it still."</div>
<div><br></div><div>- --Henry David Thoreau</div><div>-----BEGIN PGP SIGNATURE-----</div><div>Version: GnuPG v1.4.12 (Darwin)</div><div><br></div><div>iQEcBAEBAgAGBQJQTOYSAAoJEKUwgjDmsw1zb3YH/0gwZNJkD2clekXb58GDrWLv</div>
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</div>
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