Defeating keyless entry front door locks.

I’m the least mathey person I know. My bio will attest to that – my skills are terrible but my curiousity is high. There’s a certain magic to numbers that I get a glimpse of every now again when I manage to win a struggle with them and it’s compelling to me. Math is a representation of data and while me and Math don’t along very well, me and Data are best bros. I spend my days mucking about in log files on other people’s systems looking for reasons, root causes, and footprints. The trails become clear once you tame the data and turn thousands of unruly log lines into succint sorted output. These same techniques are used by good guys and bad guys alike and from them we learn that some things are truly hard. We also learn that some things only look hard, but really aren’t.

Four digit numbers crop up repeatedly in our society. In the late 1990’s I had a TD bank account and my bank card had a 6-digit PIN. That did not last long because the international consortium of bankey people standardized on 4-digits for PINS which is too bad because that exponentially decreased the security of my PIN. Overnight the odds of guessing my PIN plummeted from 1 in 1,000,000 to 1 in 10,000. But, hey, the bankey heads know what they’re doing, right? But I digress…

I’m not sure how we landed on 4 digits, but that frequency turns up all over the place. My bank card PIN is 4-digits, my credit card PINs are 4 digits, even my front door lock is 4 digits. That begs the question: how long would it take to guess the code to open my front door? Let’s ask math.

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Jon Watson – PGP Key

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