# Least likely to be tried 3 digit combination?

(I think this is closer to a poll than factual, but…)

Anyway, I got a new cheap-o lock that lets me set a three digit combination, and it made me wonder what the least likely three digit number that some random would-be thief would try.

Obviously you should avoid things like 123 or 000 or 911 or any other number that have acquired ‘significance.’

Then you have to allow for people who would brute force it. So 158 will be hit on more quickly than 856, say. Unless your thief smartly starts from 999.

Then it seems to me people have a bias to pick odd numbers whenever you ask someone to pick a number between 1 and 10. So 484 might be ‘better’ than 379 – or else that’s just a wrong impression I’ve gotten.

Anyway. The challenge is to set the combination to what you think is the last number a thief would try. What’s your guess?

I seriously doubt a single thief ever bothers with trying to guess the combination. They just look at the lock, and if they have bolt cutters, they cut it. If not, they leave it alone and move on to an easier target.

Nor do thieves try to guess passwords. They call up a help line instead and will try to pretend to be you and get the password reset. Or they stick a keystroke logging device on your keyboard so they will know whatever it is that you typed.

If you really want to be clever, look at a phone, and avoid numbers that spell any word that might be meaningful for you. You know, avoid 262 if your name is Bob, or it’s well known that you are a huge fan of Bob Newhart.

Personally, I’d pick 666. People are really superstitious, and think that other people are equally superstitious, and would avoid that number. Also, easy to remember.

There’s quite a few studies on human randomness. One study found that 2,1,9,6 were most common [1]. There’s other studies that you can find and read that look at it in a lot of interesting ways (difference in value between successive numbers, tendency for numbers to be pick in increasing or decreasing sequence, etc). Overall though I don’t think you can reach a particular conclusion as I don’t think it is known. I do recall, but I can’t find the paper now, that humans have a strong tendency to not pick the same number in a row.

[1] Schulz, M. A., Schmalbach, B., Brugger, P., & Witt, K. (2012). Analysing humanly generated random number sequences: a pattern-based approach. PloS one, 7(7), e41531.

I imagine a fair number of people use calendar dates (birthdays, anniversaries etc). And if they do, the 2nd number must be 0, 1, 2 or 3. And of those, 0-2 are much more likely than 3.

“The World’s Most Popular Numbers” is a piece about the relative popularity of different numbers.

Thieves use bolt cutters and angle grinders. The combination doesn’t matter.

A “cheap lock” and you think a real world thief is going to sit around trying to puzzle out lock combinations vs cutting or smashing it open?

There is one situation where picking uncommon numbers pays off: lotteries. You don’t improve the chance of winning, but if you do win, there will be fewer winners to share the prize with.

You might also be surprised to find out how easy it is to open many 3-digit locks without brute forcing the combo or cutting off the lock. Most, at least in my experience, are so shittily made you can “feel” out the combo by pulling on the latch and spinning the dials. Or you can use a little pin or something as a “feeler” to find the notches in the disk of the combo. I found one in my wife’s car and managed to get it open while waiting for the lights to change, no tools involved. That said, most thiefs are not going to bother doing it in a way that involves some skill.

Supposedly* you pretty much just have to pick number that don’t appear in dates (above 31) to get out of the “lots of duplicates” pools: a surprisingly large number of people use the dates of important events as their “go to” lottery numbers.

*These days, I spend an awful lot of time fact-checking stuff. This doesn’t seem worth it. So I could be LYING TO YOU ALL! Muahahahahahahahaha!

I know. I was a locksmith for a couple of years and I can open just about any padlock you put in front of me. Some, even those with a famous brand name, will pop right open with little more than a light tap of a screwdriver butt in the right spot.

But messing with padlocks was just something we did around the shop for fun; on a job, it’s just not worth the time to mess around with trying to open one non-destructively. The things are so cheap that if we cut yours off, we’d just give you another one for free.

I came across a Master Lock 3 digit luggage (TSA keyed) lock recently. Took a minute or so to open it by feel.

Bolt cutters aren’t always needed.

This was out of idle curiosity about the numbers rather than any genuine security concern. The lock in question is going onto a bike carrier thingy, a big part of the body of which is some sort of fabric-y stuff. Anyone who seriously wants to get into it will more likely use a knife than anything else. (For that matter, they’re more likely to want to just steal the entire bike anyway.) The lock will hopefully discourage bored grade school kids from casually pawing through my stuff while it’s parked outside the library.

While I was reading the instructions on how to set the combination, I got to thinking of all the contemptuous comments I’ve seen about people who leave the default password on their routers or use ‘12345’ as their passwords and the like. So, if that is the stupidest number you could use, what’s the opposite?

I settled on ‘665’ just to be contrary. (Sssh! Don’t tell!)

No matter what combination you set, it will always be the last number a thief tries (if he tries it at all).

That would seem to imply that if a thief tries, he (or she) will keep trying until they get the right combination.

My rule is to enter the same number 100 times.

It decreases my expected return, but if I do win, it will really upset anyone else who entered the same number just once.

Thieves are not very analyrical, they are more likely to start with the easiest approach. Which means starting with 000 and going 001, 002, etc. Very unlikely they would atart at 999 and work down. So 998 might be the best. It would not take even a stupid thief very long to figure out that trying random numbers willnot work, aside from the defect of having to chane three digits every time, instead of just one digit to the next on in order. First, though, they would try repetitions (222, 333), and then sequences (123, 234), then multiples (200, 300)because most people would set it at an easy number to remember, so I wouldn’t use one of those;

So if the purpose is to stymie a methodical thief, I’d use 998. But I would estimate the chances of the thief also thinking of that, and starting at 999 and working down as maybe one in 5, then I’d use 799…

I would guess that’s one of the most popular, as would pretty much any repeating three-digit combo be, but especially that one.

Maybe not quite the same thing, but we can probably get some hints from looking at the most popular 3-digit internet combinations. The most popular is, predictably, 123. Number two is 666.

I guess if we read the OP’s question closely, it’s a subtly different question than “what is the least popular 3-digit combination on a lock.”

I’d also suggest to avoid anything which has a number from 01-31 as a substring, (the first 2 or last 2 digits) because all those numbers could represent a calendar date, (with the other 1-9 as the month from January to September.) And there are probably lots of people who’d pick their birthday or anniversary date as their combination that way.