I saw this lock at Walmart for $8 and couldn’t resist, since its so different than regular combination locks. 

Operation

Operating the lock is amazingly simple and elegant.  Rather than rotating the dial like a traditional lock you push it in the cardinal directions.  This has two big benefits.  Firstly it requires much less dexterity to use then a traditional combination since you only have the be able to push the lock in 4 directions rather than be able to rotate the lock to 39 different angles.  Secondly it allows you to enter even fairly long combinations in under 10 seconds.  The lock is also user settable to any combination you want, in less than 30 seconds.  (Assuming you don’t choose a 37 move combo or something)

How it works

The internals of the lock are truly clever.  I won’t bother going over them since there is this nice pdf that already does that.  And there is this great flash visualizer that shows you how the internals of the lock work in operation.

Security

Because of the way the lock works there are only 7,501 states the internal mechanism can be in.   So although there are lots, 4^8, combinations of length 8 all of them map to one of the 7,501 states.  More troubling however is that a combination of length 8 may produced a state that is the same as a combination of length 4.  The table below summarizes the probable ‘badness’ of combos of different lengths.  It shows that combos of length 7 seem to be the sweet spot.

*Bad combos mean a combination that can be open by another combination shorter than 5 moves.

Since all the combinations of length 4 or less can be tried in about 20 minutes, 249*5sec, having a combination that can be open with a combination of 4 or less opens you up to a brute force attack.  Unfortunately these bad combos are not simple to recognize as such.  For instance the combo up,up,right,up,down,down,left,right is the same as right,right,right,right. 

Conclusion

Although there is a small chance, that you can accidently pick a bad combination for the advertised purpose of protecting a high school locker it should be more than adequate security and the easy of use is much better than a traditional lock.

I currently remote desktoping into a computer approximately 2 feet in front of me so I don’t have to lean to the left to grab the keyboard.   Its little moments like this when you remember why you love technology

A couple of months ago an extension bit broke off in my Bosch PS10 drill driver. The picture below shows the part that got stuck – I couldn’t mange to extract it with pliers or tweezers; so I set about dissembling the drill.

Since most of my experience dissembling things is with various consumer electronics  this was a night and day comparison.   You can clearly tell the bosch was designed to be serviced.  First off the screws holding the housing together were clearly visible – none of this hiding behind rubber feet or anything.  The only small complication was that after taking out all the screws there was a little white clip which slid into a slot in the bottom holding the two halves together.  Since that area is fairly thin I assume there wasn’t enough material to use a screw.

After the clip issue everything was smooth sailing.  Another example of the serviceability of the bosch with the housing removed all the components just slid out of their various slots and cubby holes.  Not a single funny little snap together connection to be found.  I found it pretty interesting how the control components worked – from the outside I would have expected them to be more complex.  All except for the clutch control they were just simple switches.  The clutch control seemed to be some sort of linear conditional resistor which was neat. Here’s a picture after I removed the innards from the housing with the control components labeled and arrows indicating where they came from.

Now that everything was exposed it was on to the chuck.  There are four screws holding it together.  Once those are removed the two halves come apart and you can remove it from the motor assembly.  Turns out everything is held in place by the housing and so with it off you can just pop out all the parts.  At this point I was able to push out the broken bit end out from the back as shown in the photo.

After that it only took about half an hour to put everything back together.  Most of that was spent screwing around with the chuck assembly.  Since its held together entirely by the housing itself and has 5 or 6 parts it required some manual dexterity to hold in the right position.  Even though the reassembly process was a little tricky overall I am very pleased.  Since the disassembly process was relatively easy I can always clean the mechanicals or add grease if I feel like it which is reassuring.

Earlier today I was trying to edit one of my posts using live writer. But I kept getting this error.

So I open up firefox and try to open my blog and get back a nice 404 error – not good!  I had been playing with installing some software on the site a few days ago and figured maybe I had messed something up along the way.  But after 15 minutes or so I couldn’t figure anything out so I fire off a support request to my hosting service Dreamhost.  Since the web site is just for my blog I gave it low level priority and didn’t really expect a response for a couple of hours given that its was a Saturday night.  However much to my surprise I got a reply in about 15 minutes from Dreamhost support saying everything is backup and running.  Now that’s what I call service!  Considering that I have had this site a little over a year and this is my first issue I must say I am pretty happy.  So in conclusion.

Thanks Dreamhost!

*Note – I didn’t receive any incentive, except for good service, to write this post.