[RC5] 40 bit encryption

Paul Goyette paul at whooppee.com
Fri Mar 15 09:31:10 EST 2002


Comparing the dnetc client's key rate isn't really useful here.

1. The client does not completely decode the message, it just tries
   each key to see if the first few bytes of the result matches the
   known text.

2. Aha!  dnetc knows what the answer is, so all we have to do is
   find a key that gives us the right answer.  In your situation,
   you are asking how long it would take to decode an _unknown_
   message, and that has to take a lot longer, especially since you
   probably won't know that you've succeeded!

On Fri, 15 Mar 2002, Jeff Gilchrist wrote:

> Quoting "Brad T." <bradtod at rocketmail.com>:
>
> > how long would it take to crack 40bit encryption? Assuming a Athlon TB
> > 1.4ghz computer was used. Some web sites still use this level of
> > security so how safe are they?
>
> Do you have this Athlon machine?  By 40bit encryption, I'm guessing you are
> referring specifically to RC5 40bit?  Run the d.net client and see how many
> keys/sec your machine will do.
>
> According to the D.Net benchmark pages, a TBird 1.4GHz will do about 5 million
> keys/second.  A 40 bit key has 2^40 keys = 1,099,511,627,776 keys.  It would
> take that machine 2^40 keys divided by 4,986,524 keys/sec = 220,496 seconds =
> 61.25 hours.
>
> To guarentee a find it would take 2.5 days but statistically you only need to
> check about half the keys so 1.25 days which is pretty darn fast.  Just add a
> few machines and that is down to hours (ie: there is little security at all).
>
> A new Athlon XP 1800 (I'm guessing that is the 1800+ which is not actually 1800
> MHz) will do 5,669,816 keys/sec would only require 2.25 days total to crack
> 40bit.
>
> Regards,
> Jeff.
>
>
> -------------------------------------------------
> This mail sent through IMP: http://horde.org/imp/
> --
> To unsubscribe, send 'unsubscribe rc5' to majordomo at lists.distributed.net
> rc5-digest subscribers replace rc5 with rc5-digest
>
>

----------------------------------------------------------------------
|   Paul Goyette   | PGP DSS Key fingerprint: |  E-mail addresses:   |
| Network Engineer | 9DC5 05CF 1AE7 DC42 CCC6 |  paul at whooppee.com   |
|  & World Cruiser | 6858 051E 7AD2 A6B2 4954 | pgoyette at juniper.net |
----------------------------------------------------------------------

--
To unsubscribe, send 'unsubscribe rc5' to majordomo at lists.distributed.net
rc5-digest subscribers replace rc5 with rc5-digest



More information about the rc5 mailing list