What exactly does the rc5 client do?

[dennilfloss]

Onof my herd asked me what exactly is rc5 and how does the client work (i.e. what does it really do)? Being barely rc5 literate myself, I decided to let the experts speak and told him I'd post a thread here. So let the cryptologists and programmers have their say.

Cheers

Denis

 

[TwoFace]

dennil:

As I've understood it it's really just a brute force kinda way to do things...

The people who have issued the contest (I don't remember who that are at the moment ) have encrypted a message using a 64bit key and the message starts with a line that goes something like this: "The message is....". What the DNet client is doing is just trying every key possible to see if it can get that sentence from the message. If someone gets that, the client will let the DNet servers know and DNet will try to decrypt the entire message and if it comes out as plain text the key is found.

I could be wrong about some details here, but I think I've got the important parts covered...

Hope this info helps some, and I'm sure there will be others in here and reply further to correct me

With love and respect your fellow TA member

Two-Face

 

[kranky]

I'll bet Gustavus could give a definitive explanation.

 

[dennilfloss]

Let's hope that our elite friend reads this thread and feels inclined to share his profound wisdom with us mere mortals.

 

[JHutch]

TwoFace has it correct. The client just brute-force checks every possible key...

If you want a more detailed explanation of the exact steps the client takes to make this check, the source code for the decrypt is available on distributed.net's website.

JHutch

 

[nickdakick]

<< with us mere mortals >>


I don't think so, we're Borg man !

 

[ss59]

RC5 is a public key encryption engine. When you generate an encryption key, 2 keys are made. The public and the private. You post your public key to your friends. If bob wants to send you an encrypted message he will use your public key to do it. you can then decipher the message to read it's contents. Only your private key can decrypt the message, hence only one key will give the right answer to the competition. Since the encrypted and decrypted message are know we have to find the right key that deciphers the encrypted one. that's basically what it does. Dnet uses a pretty dumb method i think, a better one would be to attack the encrypted message or to use the public key and attack that. Hope this helps here are some links for more info:

The RSA Laboratories Secret-Key Challenge
RSA Laboratories' Frequently Asked Questions
Detailed papers (PS and tex) describing the RC5 algorithm