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 Forum index » Diversions » Perplex City Puzzle Cards » PXC: Silver Puzzle Cards
[PUZZLE] #251 - Silver - The Thirteenth Labour
Moderators: AnthraX101, bagsbee, BrianEnigma, cassandra, Giskard, lhall, Mikeyj, myf, poozle, RobMagus, xnbomb
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oliverkeers13
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Joined: 23 May 2005
Posts: 917
Location: London, UK

 		This might seem stupid, but has someone emailed Kurt to ask, he seems like the helpful (and deceptive) sort, so might be willing to help us!
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PostPosted: Wed Jul 20, 2005 11:01 am
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BrianEnigmaModerator
Entrenched


Joined: 05 Oct 2003
Posts: 1199
Location: Pacific Northwest
BovineOne wrote:
Here is the code I used for the distributed.net "RC5-64" contest (RC5-32/12/8, ie: 64-bit key, 32-bit block):
http://www1.distributed.net/~bovine/bovine-rc5-64.cpp


Hmmm... I was kind of hoping to find something that was RC5-64/*/*. There is a lot out there that is RC5-32/*/*. While I could probably convert the 32 bit word code to 64 bit size code, I am not sure how comfortable I would be in doing so. I would be worried that in my dim understanding of of the innerworkings of this particular shared-secret algorithm, I would make some kind of fundamental mistake, thereby wasting a lot of computational time. All of my professional work with cryptography to this point has been working with APIs into dual-key libraries as well as reading/writing PKCS files.
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PostPosted: Fri Jul 22, 2005 1:29 pm
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Scott
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Joined: 11 Sep 2004
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Location: 390 Chestnut Ridge Rd, Rochester NY, 14624, USA

 		This is all sort of over my head. But is the idea to build a distributed client task to run which will decrypt this puzzle? I can lend a bunch of CPU cycles to the task, if that's the intention.
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PostPosted: Fri Jul 22, 2005 2:40 pm
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madam o'brien
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Joined: 26 Apr 2005
Posts: 31
Quote:
But is the idea to build a distributed client task to run which will decrypt this puzzle?


I don't think so. That would be too hard. The folks at disributed net took 1757 days to find do their decypt of RC5 with a 8 byte key.
That was 3 years ago but the benefit of faster processors will be offset by the fact that we are using the slower 64 bit (half-)block version and, more, significantly by the difficulty in getting such a large network working.
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PostPosted: Fri Jul 22, 2005 3:08 pm
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tanner
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Joined: 21 May 2003
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oliverkeers13 wrote:
This might seem stupid, but has someone emailed Kurt to ask, he seems like the helpful (and deceptive) sort, so might be willing to help us!


i find it really sad that you should give up so quickly -- how much pride for earthlings if we keep asking for help -- time we started to work this stuff out for ourselves Very Happy
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PostPosted: Fri Jul 22, 2005 4:58 pm
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oliverkeers13
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Joined: 23 May 2005
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Location: London, UK

 		I haven't, but decipering 64 bit encryption is a herculean labour!
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"To be in opposition is not to be a nihilist" CH
"im iver an idiot or a genus" Dekuprince
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PostPosted: Fri Jul 22, 2005 5:03 pm
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Riiick
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Joined: 29 Apr 2005
Posts: 82
Location: Canterbury, Kent, UK

 		The Wikipedia page for RC5 states:
Quote:
12-round RC5 (with 64-bit blocks) is susceptible to a differential attack using 2^44 chosen plaintexts (Biryukov and Kushilevitz, 1998).


The cipher on the cards (i believe) is 12 round RC5 with 64 bit blocks.

Does this mean 17592186044416 different combinations have to be tried? If so how long would this take?

PostPosted: Thu Aug 04, 2005 7:41 pm
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diddymac
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Joined: 11 Jul 2005
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 		A long time.
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PostPosted: Thu Aug 04, 2005 8:01 pm
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Riiick
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Joined: 29 Apr 2005
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Location: Canterbury, Kent, UK

 		We need code to decrypt 64 bit block size RC4-64 first. It could just be the key is the same as www.distributed.net used (0x63DE7DC154F4D039) as SteveC guessed.

Surely there must be some kind of existing free code for this (or even a commercial program we can try an eval of). Not that google has proved very useful in finding anything...

PostPosted: Fri Aug 05, 2005 7:06 am
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chocshake
Boot

Joined: 14 May 2005
Posts: 12

 		just been looking around and found this

http://www.softpedia.com/progDownload/Krypt-Download-21054.html

program available for a free trail download. it says that it decrypts RC4, but does it need to be more specific then that? (dont know a huge amount about this subject.....)

PostPosted: Fri Aug 05, 2005 8:44 am
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SteveC
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Joined: 05 May 2005
Posts: 381
Riiick wrote:
The Wikipedia page for RC5 states:
Quote:
12-round RC5 (with 64-bit blocks) is susceptible to a differential attack using 2^44 chosen plaintexts (Biryukov and Kushilevitz, 1998).


The cipher on the cards (i believe) is 12 round RC5 with 64 bit blocks.

Does this mean 17592186044416 different combinations have to be tried? If so how long would this take?


If this is the case, that's not such a huge number. When my computers were doing the RC5 I went through about ten times that, over the period of a year or two, but if 20 or 30 of us hit at it, it's perfectly possible. Computers are significantly faster now..

Returns to the problem that we have with this and with the solitaire puzzle however, both have weaknesses in these examples, but we don't have cryptanalysts on board to help us! Given the information we have, we couldn't even decode it with a known key!

PostPosted: Sat Aug 06, 2005 3:40 pm
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Macavity
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Joined: 25 Jul 2004
Posts: 883
Location: UNSC Comm Relay Station Alpha, West Shokan, NY

 		Here's a thought - we might try asking around on the Def Con fora.

Why?

The guys there are some of the primo hackers in the world. If anyone'd be able to find an RC5-64/12/8 decrypt program, it would be them. (Heck, they might even crack the code for us, if we ask nicely enough.)

One caveat, though: One guy there who goes by the name of highwizard can be a real b@st@rd at times. The rest of the time, he's just hostile (especially towards newcomers).
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PostPosted: Sat Aug 06, 2005 5:28 pm
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neuromancer
Decorated


Joined: 04 Aug 2005
Posts: 168
Location: Birmingham, UK

 		Massively Parallel Computing Cluster
Hi,

This may or may not help but what about building a simple (but powerful) cluster computer AKA supercomputer like this.
Basically you can get a few old pc base-units, from somewhere like this place near me: Speedie Computers. Network them all together with a switch, and then install an OS like ClusterKnoppix on all of them. There's an article on how to do it here.
You then make one of the units your 'master' node which controls all of the others. You will end up with a system that has a power equal to the sum of the individual nodes' processing power - some overhead. If 1 of us can get a supercomputer then we can have the decoding app running on it. Won't be an instantaneous decode but will definitely be faster than a single system doing it...perhaps....I'm willing to help write the app.
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PostPosted: Mon Aug 08, 2005 1:56 pm
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braincoffee.com
Boot


Joined: 09 Aug 2005
Posts: 11
Location: braincoffee.com

 		connection w/ the forever foe card?
i know approximately zippo about cryptography, but might it be possible that the 100 characters on the autographed yellow forever foe cards could be connected to the key for this code?
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the cards we have/need

PostPosted: Sat Aug 13, 2005 10:05 pm
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Scantron
Greenhorn


Joined: 08 Aug 2005
Posts: 7
Location: Sherman Oaks, CA

 		A Few Years
I just noticed the wording on the Perplexcity.com FAQ:

How many cards will there be in total?
The first season of Perplex City will comprise 256 cards.

Maybe some of these are meant to take over a year to solve. Awfully daunting, isn't it?

PostPosted: Sun Aug 14, 2005 5:05 pm
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