[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

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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