Aral Balkan

The "my fine is" meme asks people to calculate the total fine for various personal indiscretions that they've engaged in and post the aggregate result publicly.

Smoking pot, for example, nets you a $10 fine whereas having sex in church sets you back $25. You add up the various fines for all the offenses you committed to reach the value of your final fine and publish it publicly (e.g., on Facebook or your blog).

The idea is that the higher your final fine, the naughtier you've been and yet no one knows exactly what you've done so your secrets are safe.

A little harmless fun, surely.

But if the originator of the meme had been less scrupulous or better versed in mathematics (and, more than likely, both), it could have led to a lot of potentially embarrassing admissions. How?

1. Use only prime numbers for the fine amounts (e.g., $3, $5, $7, $19, $43, etc.)
2. Instead of asking people to sum the total, ask them to find the product of their answers (i.e., multiply them).

So, say that smoking pot had a $3 fine and having sex in church set you back $5. If you had engaged in both these offenses, your fine would be $15.

If you posted this publicly, thinking that the aggregate amount hid your true dealings, you would be in for a rude awakening at some point since multiplying two prime numbers results in a composite number that is divisible by those two numbers alone (as well as 1 and itself). So there's only one way that $15 could be read as: you smoked pot and had sex in church.

(It would still be up to people's imaginations, however, if you did both at the same time.)

Similarly, if you had partaken in the $3, $5, and $7 offenses, your total fine would be $105. A seemingly innocent number but one that can only be divided by those three numbers, their various composites, 1, and itself. So publishing that single number would have been essentially the same as owning up to each of the separate offenses publicly in a list.

All this to say that someone could have used this meme, in a slightly altered format, as a widespread social engineering hack to get people to reveal their most personal details while lulled into thinking that they were publishing an aggregate and rather less revealing number.

Comments

• I like this post and totally agree, i was reading the "my fine" page last night and thinking similar things. There are two that you can reveal exactly what that fine was for at present but your post was still an interesting read. Thanks.... :-)

  by Joe Stubbs on 2010-01-13 08:41:32

• You're so cunning, Aral!

  by Paul Annett on 2010-01-13 01:02:43

• Ah, well at least you can tell who pisses in swimming pools. That is the only 50 cent fine. So if someone says "my fine is $xxx.50" you know what they have been doing when you thought they were just treading water.

  by Jane De Ath on 2010-01-13 15:06:55

• sorry.. didnt catch the other comments....

  by John on 2010-01-14 17:11:50

• Just had the same idea, posted it to Twitter, and got pointed here! You wouldn't need primes being multiplied though; just use $(n^2) for each answer - essentially, represent the answers as a bitfield.

  by Tom on 2010-01-14 13:28:46

• Actually - prime numbers will not always give you a unique result. Take for example $3 + $5 + $11 = $19 - As Tom said the only way to get a unique result is to use powers of 2, the way the binary system works that computers use.

  by Mario Klingemann on 2010-01-14 13:37:33

• Very clever indeed. I'll be wary of any meme's coming from your direction Aral.

  by Ben on 2010-01-14 10:40:54

• wot will my fine be?

  by john thurgood on 2010-01-14 15:38:31

• It's even simpler than that... ... only two of the offences were for less than $1 - one for $0.10 and one for $0.50. Anybody posting a total with a suffix of .10 , .50 , or .60 is revealing which of those two offences they'd committed. I am very cynical, but I think this was intentional.....

  by John on 2010-01-14 17:10:40

• Hey guys, Thanks for the $0.50 and $0.10 updates; nice way of sneaking those in there (wonder if it was intentional) Mario: Ah, but I wasn't saying to add them but to multiply them (so, in your example, it would be $3 * $5 * $11). Mind you, I like Tom's way; nice one! :)

  by Aral on 2010-01-15 16:40:23

• thanks aral. süper

  by rüya yorumları on 2010-01-17 12:29:48

• Perhaps I'm not very well versed in mathematics- how does this work? "So, say that smoking pot had a $3 fine and having sex in church set you back $5. If you had engaged in both these offenses, your fine would be $15." that makes $8 surely????

  by Mo on 2010-01-18 14:32:31

• Well already the fine for peeing in a pool is £0.50p and kissing someone who's name you didnt know is £0.10p so you know instantly who did those because nothing else adds pennies.

  by Kal on 2010-01-18 13:26:32

• Awesome piece :) I've been worried that people can figure out what I've done, haha!

  by Daniel on 2010-01-18 18:56:08

• There are a few that already fall into we know what you've been up to tricky kissing someone who you don't know their name nets you $.10 and peeing in a pool is $.50 both can be easily identified. Anothing method would of been increaseing the fine by powers of 2. Given the number of rules you'd end up with the worse acts in the thousands bracket but again could be broken down at a later point.

  by Nutter on 2010-01-13 12:02:21

• Hey Mo, if you re-read the article, you'll see that I state that the revised rules would make you multiply, not add the numbers :)

  by Aral on 2010-01-22 11:35:38

• Numbers trick were common place during recess when I grew up, nerds would pass for geniuses guessing the 'secret' answers of their less math-oriented classmates. What has changed is that people fool themselves into thinking a little revelation about themselves here and there can't come back to bite them in the proverbial backside. Social networking and engineering can be devastating tools in the hands of some. the net doesn't forget.

  by Adrian Clot on 2010-01-23 02:36:36

• Hey, I had the exact same thought when I saw this meme. It's an opportunity lost! Perhaps someone should make an FB app out of this...

  by Udo on 2010-10-20 13:16:45