PureGin.org

While waiting in line to buy a coffee today, I noticed a poster listing "Top 5 Tips to prevent bike theft". One of those tips was "Engrave your driver's license number on the frame of your bike". This (and variants) seems to be routinely offered incredibly bad advice, freely given by those who should know better, e.g., police forces, security experts, etc. Why is this bad? Consider the following scenario.

1. Your treasured bike, with D/L carefully inscribed, is stolen
2. You put up posters, and post descriptions of the bike to your various social networks, hoping to recover your baby
3. Evil dude who stole your bike notices your posters and/or posts ("use your social network for fun and (criminal) profits") and discovers your name/phone number/email.
4. A little research reveals your birthdate (wasn't it nice getting birthday greetings from all your friends on Facebook?)
5. Evil dude applies for a credit card in your name, using your birthdate and D/L as primary ID, and has a lovely all expenses paid vacation in Las Vegas

My advice: do not, under any circumstances, use any personal identification numbers to label valuables which might be stolen.

Generally, bikes already have serial numbers. Make a note of this with your purchase receipt/documentation for the bike and keep it somewhere you'll be able to find it. "But", you argue, "evil dude could just as easily provide faked evidence of ownership. There's nothing linking me personally to the bike!". I don't particularly buy this... I don't see anyone advising me to engrave my driver's license on my car, for example. This might make for an amusing comedy skit though... "Uh, driver's licence, officer? I think it's engraved down there under the car somewhere...".

If you must have something provably personalized to you on the bike, engrave a cryptographic hash of the information instead. For example, if your drivers' licence number is "12345678", the md5 signature (hash) is "23cdc18507b52418db7740cbb5543e54". That's 32 characters to engrave rather than 8, but hey, your baby is worth it, right?

How do you find the hash of your D/L? Glad you asked. On your mac or BSD machine, open a terminal window and type

echo 12345678 | md5


On other flavours of Unix or GNU/Linux, try md5sum rather than md5.

If you are running Windows, you'll have to do some research. You might find md5summer useful; I've not tried it. This or this may be better long-term solutions for you.

There are web-based services available which will compute cryptographic hashes for you. If you've been paying attention, you'll understand why you don't want to use these.

All of the above may itself be bad advice. Md5 is not regarded as particularly secure anymore. So, if your bike has been stolen by the KGB, CSIS, CIA, DHS, NSA, etc, you're probably foobar'd. But then, this may be symptomatic of larger troubles.