Programming 3 - My method takes a long time

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Programming 3 - My method takes a long time

Post by J3LR0M on Mon Feb 16, 2009 5:49 am
([msg=17998]see Programming 3 - My method takes a long time[/msg])

I've been working on programming three for some time, and have successfully written a program in c++ which can partially bruteforce the serial numbers. The problem is, my method takes an extremely long time, and I only have 300 seconds. Basically, it starts by brute forcing the initial intMD5Total value and the first 6 values of the first serial number. It is then able to verify whether the combination works by using the -OEM- part of the serial. Several dead ends are also cut off by the fact that the fourth character has to be '-'. I've found that on average there are about 2000 possible combinations up to the third character (including the brute forcing of the initial total). This gives me a keyspace of 2000*35*35*35, which is about 900 million. Unfortunately this kind of keyspace takes hours to work through. Either my method is completely wrong, or there is a shortcut I have missed. Could somebody please shed some light on this for me?

Cheers

-- Mon Feb 16, 2009 2:00 pm --

Since i wrote the first post, i've managed to optimize my method to get the first 6 charactors of the first serial in a few mins. It's now starting to look like I may just be able to tackle the problem with my method with some optimization.
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Re: Programming 3 - My method takes a long time

Post by AgentSmithers on Thu Feb 19, 2009 3:27 pm
([msg=18245]see Re: Programming 3 - My method takes a long time[/msg])

Well cant complain if you write it in ASM it might be faster but dont want to waste time on that, How are you brute forcing the numbers are you using ASCII 49+ for the Text Numbers or are you doing Further conversions?
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Re: Programming 3 - My method takes a long time

Post by J3LR0M on Thu Feb 19, 2009 4:50 pm
([msg=18247]see Re: Programming 3 - My method takes a long time[/msg])

I completed it in the end with ages to spare. The reason for this was finding another way to reduce the key space which I had overlooked. The mission was fun, but didn't half take a long time! I rather suspect it is underrated in terms of difficulty.
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Re: Programming 3 - My method takes a long time

Post by BhaaL on Fri Feb 20, 2009 9:32 am
([msg=18285]see Re: Programming 3 - My method takes a long time[/msg])

The most (only?) difficult part of this mission is identifying the things you know, and designing your brute-forcing algorithm to take those things into account.
Neither of the missions should require you to write them in a highly performant way (such as ASM), they only require you to write them in a smart manner.
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