brute-force cipher cracking?

Question

Powerful processors are becoming increasingly cheap nowadays and many of the most popular cryptographic systems in use use short keys (less than 128 bits, say) suppose I wanted to test how long it would take to crack a cipher using a brute force approach by physically linking off-the-shelf processors and using a custom written app to do it
(written in C/C++ or assembler for speed). How would I connect the processors and how many would I need to do it in
a reasonable time? Is it even possible? This is basically what the EFF did in '98 with their DES cracker but they used custom-built processors. What about off-the-shelf processors running a dedicated application? http://www.copacobana.org/ uses FPGAs is there an advantage to doing this?

Answer 1

So you want to create your own processor-rack huh? theres a book on amazon called Building Extreme PC's (Modding guide.) I



I am not sure they have actually cracked DES..I had read an article long time back about a group who's into 'Distributed Cracking' (somewhat like SITI project) and were able to crack BlowFish...



But I tell you 98...is like a decade back...and your PC today has a capacity of a 98 supercomputer..but still DES..it would take years and years to crack it.



(how old are you btw?)

Answer 2

Wow, you really know something about the question you are asking.



As for linking up the processors, I truly don't know. I'm not a hardware guy (I do plan on trying to build my own computer sometime, with Linux of course).



If you had multiple boxes sitting around, you could set up John or your program to run simultaneously on the multiple boxes.



The problem with Copacobana is that it only supports 64 bit keys, which is really nothing. It seems unimpressive for the cost, although the name is catchy.



You seem like the person who would be smart enough to Google, but you never know.



Here is what I would do: Get your nice dual-core comp and but from a live CD or a Linux partition. Windows just runs to much stuff that you don't need hogging those CPU cycles. Run John the Ripper. I would assume that you know the program, if you are in to not only cryptography but also programming. And as I recall, John can be ran on two processors and I know that it can be ran on multiple boxes.



To the first answerer: You are correct DES can't be cracked, to my knowledge, however, just like LM and MD5 hashes (which are one-way algorithms and cannot be cracked) you can brute force it, which is what he was asking about.



I will return to this question, as I would like to see some of the responses you get, but feel free to email me about anything.



Good Luck and Great Question.

Answer 3

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