[RC5] Cracking 40 bits in realtime

Matt Perry matt at primefactor.com
Sat Jan 3 09:52:24 EST 1998


On Fri, 2 Jan 1998, Greg Wooledge wrote:

> Matt Perry (matt at primefactor.com) wrote:
> 
> > My suggestion involved people like you and me submitting 40 bit encrypted
> > message to which we know the plain text.  Just like RSA.  But EVERYONE can
> > do it.  I'll submit the first and I'll tell you what the first 30
> > characters of the message are.  Just like RSA.  My neighbours will be
> > next, submitting their own 40 bit encrypted message to be cracked.
> 
> And after a week or so, John Q. Hax0r will submit an encrypted message
> which just happens to contain a sniffed credit card transaction.
> 
> I have to agree with Skip here.  As neat as this concept is, it's way too
> open to abuse.  Distributed.net would get in a *lot* of legal trouble if
> the scenario described above took place and J.Q.H. used the credit card
> information illegally.  Chances are the 10000+ of us cracking the blocks
> wouldn't be prosecuted, simply because we're too numerous, but d.net
> would almost certainly be shut down.  I'd really hate to see that happen.

Nonesense.  It's no different than what we are doing now.  J.Q.H. will
have to know the first 30 to 40 bytes of the unencrypted message so that
we can know the winning key.  Just like we know the first few bytes of the
message of the RSA contest.  So we can find the key.  Go read my message
again.  The person submitting the block has to know part of the
unencrypted message anyway.

	There's no difference in this and the RSA contests except it's a
smaller key length and anyone, not just RSA can have their contest.
Create a message, encrypt it, tell us the first 30 characters, then we're
off.  Just like RSA.

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