Nice reasoning. How long did it take you to figure it out?
About 10 minutes :)
Hacking a parking ticket system
21–30 of 65 posts
Re: Hacking a parking ticket system
#22> I'm sure there's a bit more elegant way to find the missing thousand component, but for me it would be just quicker to do a bit of brute-forcing: The calculation the author wants is LastThreeDigits(secret*23) = 642 that is equivalent to secret * 23 == 642 (mod 1000) that is equivalent to secret * 23 + dummy * 1000 = 642 The standard method is to solve this first for 1 instead of 642 other_secret * 23 + other_dummy…
Thanks!
Re: Hacking a parking ticket system
#23The checksum algorithm they used will only produce 73 different checksums (00000000-99999999: 0-72) - and all of them even. There is space for 9999 different values. Tips to improve: f(x) = ( x * secret) mod 1000 - mod 10000 instead of mod 1000 (as mentioned in the article) - make sure the 'x' varies between 0-9999 (e.g. by splitting the number in half and adding the parts 03001909 > 0300+1909 = 2209) - make sure the…
It is probably just a barcode checksum/error code, otherwise they wouldn't have to rely on the values of the first 8 digits. Instead they should generate 4 random digits and store them in the database along with other information, then it basically works like a pin number (and xor it with a proper checksum). Edit: If it is really a checksum, it is a crappy one.
A lot of symbologies support some kind of modulo check digit. It's mostly there to detect erasure and substitution errors, because those are relatively common errors in decode. A modulo sum is better than nothing, considering that each additional digit increases the length of the barcode. If you're length-constrained, then adding more check-data is a difficult trade-off between stronger protection and smaller module size, meaning that you could add so much data that the barcode becomes too dense to print or read.
Re: Hacking a parking ticket system
#24Earlier quoted context omitted.
Many automated garages ban motorcycles because they're unable to trigger the sensor.
Or they make the barriers slightly shorter so that motorcycles can park for free.
Which they do, recognizing the fact that if there are a few motorcycles parked in your lot, it makes the whole lot look cooler.
Re: Hacking a parking ticket system
#25That was too easy.
Re: Hacking a parking ticket system
#26now the question is: why did they choose 854?
That's what I was wondering.
~$ factors 854
854: 2 x 7 x 61
Re: Hacking a parking ticket system
#27A friend of mine in college did this, but it was even simpler- there was no barcode, just a number that increased by one for each ticket sold. He went the entire year just making his own to avoid paying $3 per day. Just take the last three days tickets, increment by the average difference, print and display. When they caught him (he parked in the wrong lot or something) he admitted everything, paid $80, and offered t…
A much simpler "hack" occurred to me recently. Suppose you wanted to store your car for a long time in a gated garage that also holds ZipCars.
Drive your car in and take a ticket as normal. When it's time to leave, book a ZipCar for one hour. Grab its parking pass and use it to exit the garage with your car. Park on the street nearby, walk the pass back to the ZipCar.
Are there typically countermeasures in place for this? Match the pass to the license plate with ANPR? Don't allow an exit without a corresponding entrance? Sucks for the next person to use the ZipCar. But how will they know it was you? Are video archives good enough to find the plate associated with a particular card swipe without a ton of manual effort?
(Assume you're trying to store a car for a month or more. At a fairly normal Chicago visitor parking rate of $25 for 2 hours, that would cost $9,000.)
Re: Hacking a parking ticket system
#28A really simple "hack" of a car park with an entry barrier that issues you a ticket is that you can usually exit the car park with an unpaid ticket if it's under 10 min old. So just get a new ticket from the entrance when you want to leave. They do this so you can get out if there are no spaces. I haven't done this myself and don't condone it. You will probably get in trouble and it's not nice.
And let's add the legal term for it here, so it's clear what this "hack" actually is: Fraud.
A very relevant xkcd: https://xkcd.com/1494/.
Re: Hacking a parking ticket system
#29A really simple "hack" of a car park with an entry barrier that issues you a ticket is that you can usually exit the car park with an unpaid ticket if it's under 10 min old. So just get a new ticket from the entrance when you want to leave. They do this so you can get out if there are no spaces. I haven't done this myself and don't condone it. You will probably get in trouble and it's not nice.
> So just get a new ticket from the entrance Getting a new ticket from the printer before the barrier will be hard if your car is inside the car park. Often the ticket printer will only work if it notices a large metal object (such as a car) in front of the barrier.
Not-All-That-Interesting-But-Relevant-Story-Time:
In Santa Barbara all of the parking lots downtown where the bars are had attendants. This was before people credit card machines allowed lots to be open 24/7. Anyways, most lots had the entrance/exits at the same location so if someone pulled in to get a ticket and then backed out the attendant would notice. One lot had the entrance all by itself on the opposite side of the lot, blocked by some trees. I have many friends who would go out for a night on the town and then get someone to drive them back in the morning, pick up a ticket without entering, then leave using that fresh ticket.
Re: Hacking a parking ticket system
#30A really simple "hack" of a car park with an entry barrier that issues you a ticket is that you can usually exit the car park with an unpaid ticket if it's under 10 min old. So just get a new ticket from the entrance when you want to leave. They do this so you can get out if there are no spaces. I haven't done this myself and don't condone it. You will probably get in trouble and it's not nice.
I think this will not work with most of good systems. As there are inductor loops or sensors at the gate(ticketing machine) . Which sense a vehicle and then allow allow the machine to print a ticket. You should check your hypothesis.... But m sure there r weaker systems which don't have these checks