MovieChat Forums > Robot & Frank (2012) Discussion > Brute force would not work

Brute force would not work

posted 12 years ago by sth128
52 replies | jump to latest

So the robot says that it takes between 4 seconds and 1 hour 43 minutes to crack a 3-number combination safe. That is complete rubbish. The 4 seconds is likely the estimate for opening the safe on the first try, this means it takes the robot 4 seconds to rotate the dial 3 times. 1 hour 43 minutes equals 6,180 seconds, divided by 4 gives 1,545 trials.

A combination lock dial usually scales between 1 and 100 (search "combination lock dial" on Google and you'll see). 3 number combination means at least 100 x 99 x 99 permutations (I'm assuming you can't have 3 identical numbers). That is 980,100 possible combinations, 634 times more combinations than the trials the robot can perform in the given time.

Ignoring that "little" problem and say the robot does brute force its way through the lock, another problem with spinning the dial so many times in such a short duration is heat generation. If every 3 trials span one single revolution (that is, the equivalent of rotating the dial exactly 360 degrees), that means 326,700 revolutions over the 103 minutes, which is over 3000 RPM. Imagine spinning the lock dial at that speed for over an hour. That thing will be so frigging hot the gears would probably expand and lock the entire assembly.

Even if the safe was using a high school combination lock (ie. 30 numbers), there will still be 25,230 possible permutations, 16 times more than the 1545 trials the robot can perform in the given time.

That robot might be able to cook and garden, but it sure as *beep* can't do basic math.

[–] Youmustlearn649 12 years ago

i hope your joking mate, cause otherwise you are a complete wanker!!!

[–] sth128 12 years ago

Yes... I'm a wanker because I can tell an egregious error that violates basic math.

What kind of moron is anti-intellect? I'm a nuclear engineer so you better hope I'm not joking when it comes to technical details. For someone whose uses a name of "you must learn", you sure aren't too accepting of learning.

[–] dreamcop25 12 years ago

Let me guess you watched Space Cowboys and screamed at the movie that's impossible to get someone in space in less than 60 days!" Or A guy that age couldn't impress a young hot woman (Donald Donald Sutherland's character at the bar). Dude relax if your putting that much emphasis into a FICTIONAL movie. You either seriously need to get laid or see a shrink..or both.

[–] stabiljka 12 years ago

3 digit safe has exactly 1000 combinations. Permutations have nothing to do with it.

[–] ClintJCL 12 years ago

He is right. You are wrong. The only way to have 000 combinations is if you have 3 single-digits. The safe did not have only 10 values (0-9).

Most go up to at least 60. Three of those is 60*60*60 = 216,000. So yes, the upper bound should be 216,000 more than the lower bound. If the lower bound is 4 seconds, the upper bound should be 216,000 times 4 seconds, which happens to be exactly 10 days.

But that's just one example, with a 3-combination safe with a dial that goes up to the number 60. In combinatorics this is referred to as "60 choose 3". What you were describing (1000 combinations) is "10 choose 3".

-ClintJCL
http://clintjcl.wordpress.com/category/reviews/
http://www.flickr.com/photos/clintjcl

[–] ghost_hat 11 years ago

Why is it every nuclear engineer, brain surgeon and rocket scientist spend all their time posting things online? It's amazing how many of these people show up to argue about movies and tv shows...

[–] 11 years ago

[deleted]

[–] kb-70 11 years ago

Because we read faster than the rest of you, so it's less of an effort. Nothing special, it's just more practice. Nerds read constantly, right?

My own reading speed was 1,200 words/minute, last time I tested myself. If you're an "average American", yours is about 200. OTOH, my fine motors skills stink and I can barely catch a thrown ball...because that isn't something I ever practiced.

[–] Kuato_and_George 11 years ago

Your a wanker because you say things like "egregious error" and "anti-intellect".

For my latest movie reviews and news:http://www.hesaidshesaidreviewsite.com/

[–] special_user 12 years ago

you must be fun at parties

[–] sth128 12 years ago

Of course I'm fun at parties. I can calculate correctly the amount of beer necessary to sustain said party. Where as you probably underestimate like the robot in this film and end up having the worst party of all time.

[–] DoctorStrangelove 12 years ago

Ha! Well done.

The Doctor is out. Far out.

[–] Mrpinkeye 12 years ago

cool story bro. he still opened it tho!!! bahahaha

[–] sth128 12 years ago

No *bleep* Sherlock of course he opened it. Just because the script says the moon is square doesn't make it so. Or are you of the opinion that "if it happens on screen it must be true"?

[–] Mrpinkeye 12 years ago

i didnt hear them mention the moon once....

[–] sth128 12 years ago

That's no moon, that's YO MAMA!

[–] Mrpinkeye 12 years ago

Cool story bro

[–] tjc_2005 12 years ago

haha nuclear engineer my A$$, someone who should know better to call it Maths, not "math" dumba$$, anyway, nice comeback for such an intelligent person. Newb

[–] sth128 12 years ago

http://dictionary.reference.com/browse/math?s=t

Uh huh.

My retorts will only be as intelligent as the responses I got.

[–] jyw 12 years ago

I didn't think the robot could open the lock in that short of time either. I just didn't bother to do the numbers. Thanks for proving that I was correct.

Playing scrabble with the Infantata! Here's a tip for you, let him win!

[–] savaslikesmovies 12 years ago

This thread is interesting.

But instead of brute forcing, it could have just listened for the gates to align and open it in 5 minutes.

But if you really wanted brute force, here's one:

http://www.kvogt.com/autodialer/

you see they dramatically reduce the time due to "forbidden zones" with the lock. maybe thats what the robot takes in consideration. do we actually know the lock type?

personally if i was going to have problems with this, i would have problems with the whole movie. such as how a robot that is so advanced like the robot that they would "forget" or not bother to block it from even attempting to brute force anything. it simply should be smart enough to decide.

though the concept is that the robot is the early models of a new robot, considering the woman's robot is the regular ones.

[–] sth128 12 years ago

@savaslikesmovies

Interesting project. However the optimization only reduced one order of magnitude (ie. by 10) and the trial still took 21,000 attempts. 4 seconds (single attempt) by 21,000 attempts is still 23 hours.

Note also that this is a project developed by 2 MIT students with the aid of laptops and detailed technical knowledge, not a senile octogenarian who confuses his robot with his son wearing an astronaut helmet.

The robot in the video does dial the lock faster than the movie robot however, averaging 2 seconds per combination (11 clicks in the 26 second video). The site doesn't detail exactly how many is "a few hours". 21,000 attempts at 2 second average is still over 11 hours. The article might have misrepresented the robot's speed.

The lock used in their project is a Sargent and Greenleaf 8400, with a face dial of 0 to 99, culminating in 1,000,000 (one million) possible permutations as advertised on their own site (http://www.sargentandgreenleaf.com/MC-8400.php). This is the same number used in my calculations in the topic post.

Point is, there is NO WAY the robot can "brute force" its way into a safe as depicted in the film within the time frame given by the robot. Modern cryptology (including physical safes) are designed to combat brute force entry specifically because of the computational power we have today. This might change if and when quantum computing becomes a practical reality, but that doesn't seem likely any time soon.

[–] savaslikesmovies 12 years ago

no i think it reduced it more than that. from a comment on that page:

for the 8400 lock: no numbers between 35 & 55 for the last number, no numbers ending in 0 or 5, and no rising or falling sequences.

unless the comment is incorrect, which i haven't bothered to check. you can find more about "forbidden zones", here: http://www.crypto.com/papers/safelocks.pdf

The lever-fence design is subject to somewhat anomalous behavior if the combination of the last wheel is set
too near the point at which the nose enters the drive cam gate. Usually, the lever nose will become trapped
in the cam gate, preventing the bolt from being re-locked. More rarely, the lock will fail to open altogether.
This is the reason that the range of numbers allowable for the last combination is restricted, avoiding those
that would position the last wheel gate too close to the cam gate. This region of the dial is usually called the
forbidden zone, and applies only to the last number of the combination.

anyway those mit guys are very vague with their numbers. the safe has a finite amount of combination so it 100% possible to brute force a safe, this isn't news. the question is how long, but they seem to not even answer the only question that matters. anyway, why are you comparing frank to the mit students, it's not as if frank built the robot or even programmed it.

once you build the fastest "robot", then the only thing slowing you down is the safe, and that we don't know of.

the writer probably heard of brute force from somewhere and felt it would sound cool in the movie. obviously they have no idea about why mechanical safes are no longer used. simply because you can get in them in like 5 minutes, just by detecting the gates.

[–] sth128 12 years ago

no i think it reduced it more than that. from a comment on that page:

Well that's irrelevant as I pointed out, even at 2 seconds per attempt (as shown in video), the safe will still take over 11 hours to crack.

why are you comparing frank to the mit students, it's not as if frank built the robot or even programmed it.

Because Frank instructed the robot to crack the safe. Unless the robot comes pre-packaged with a safe-cracking subroutine, ANY information it has probably came from Frank. Therefore Frank must have detail knowledge of the safe mechanism in question.

the writer probably heard of brute force from somewhere and felt it would sound cool in the movie. obviously they have no idea about why mechanical safes are no longer used. simply because you can get in them in like 5 minutes, just by detecting the gates.

But mechanical safes are still being used. And there's nothing stopping manufacturers from making a hybrid safe where the combination actually dials a digital encryption box, negating the whole "crack by listening" thing.

I don't think the writers thought "brute force" would sound "cool" and put it in the film. The writers probably thought "robots can do stuff real fast so let's make it brute force its way into a safe". Unfortunately they lack the very basic understanding of high school statistics necessary to avoid the kind of stupidity shown in the film.

I find more and more movies these days not only ask me to suspend my disbelief, but also suspend basic logic, reasoning, science, and more or less everything else. Take for example "Taken 2" where our hero asks his daughter to draw a circle using circumference...

[–] jinstonchung 12 years ago

This thread is interesting, but I want to point out a mistake you are making. The robot is shown to have mobile connectivity. It is able to call the son without using a phone. This implies he is also connected the internet. It can easily Google information about safe picking and find things such as this MIT project. So, Frank would not be the only source of information for the robot.

[–] 12 years ago

[deleted]

[–] JackMillion 12 years ago

Ah! Nice logic.
However, you have forgotten one thing: This was a FUTURE safe! The movie took place in the FUTURE!!!! SO: who's to say that these future safes don't have the problem with heat & expanding gears?
Also - maybe the robot was smart enough to apply an algorithm to eliminate obvious duplicate or fake combinations? IE: chances are the combination wasn't 1-2-3, so maybe he didn't need to try THAT one?
See? THE FUTURE!!! It will mess you up!!!!

[–] qofreason 12 years ago

r u a robot?

[–] anvilheadsix 12 years ago

The OP really needs to get laid.

[–] girl_pearce 12 years ago

In one of his recent posts on another threat he literally wrote "I watch too much porn"