[RC5] RC5 question

Bruce Wilson bruce.wilson at distributed.net
Fri Oct 3 19:44:55 EDT 2003


Unfortunately, 128 bit RSA wouldn't be all that relevant.  SSL doesn't
use RC5, it uses RC2 or RC4, which are different algorithms.  (see
http://www.verisign.com/products/site/faq/128-bit.html#8).

You can't compare the strength of different algorithms using their bit
length.  (In particular, I think RC2 and RC4 have easier known attacks
than brute force.)  128-bit DES (if there was such a thing) would be
far weaker than 128-bit RC5.

__
Bruce Wilson <bwilson at distributed.net>
PGP KeyID: 5430B995, http://www.toomuchblue.com/ 

“I want to move to Theory. Everything works in Theory.”
    --John Cash, id Software


| -----Original Message-----
| From: rc5-bounces at lists.distributed.net 
| [mailto:rc5-bounces at lists.distributed.net] On Behalf Of 
| Daniel Quintiliani
| Sent: Friday, October 03, 2003 18:10
| To: D.net Discussion
| Subject: Re: [RC5] RC5 question
| 
| 
| On Fri, 3 Oct 2003 19:03:10 -0300, Décio Luiz Gazzoni Filho 
| <decio at revistapcs.com.br> wrote:
| 
| >
| > If you factor in new participants and Moore's Law (which 
| dictates an 
| > exponential growth of processing power with time), RC5-72 
| is doable, 
| > whereas RC5-128 is utterly hopeless, short of a very clever 
| attack on the 
| > RC5 cipher.
| >
| > Frankly I don't see the point of running a contest that has 
| absolutely no 
| > chance whatsoever of finishing. Then again, The Neo Project 
| was doing 
| > just that with the RSA factoring contests, albeit in a much 
| larger scale 
| > (meaning it was even more hopeless), and people still helped them.
| >
| > Décio
| 
| You just don't look at it as a contest. There were no prizes 
| for SETI, or 
| for our OGR, and still they're fun. I ran SETI for 3 years up 
| until last 
| summer. I knew the likelihood of me finding ET, and when the project

| finished I noticed that my name wasn't on the list of good 
| workunits, but 
| it was still a fun thing to do. (I did get annoyed later when 
| I heard that 
| they were going to delete the statistics.) Anyway, these 
| things are just 
| fun to do. I'm just suggesting that 128-bit would be more fun 
| than 72-bit 
| since it would be more relevant today.
| 
| -- 
| -Dan
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