Several students cracked the SSL RC4-40 implementation in
about 30 hours with borrowed cycles on computers around their schools.
SSL uses a slick salting mechanism to make brute force attacks like
this more difficult. However, *any* bad guy worth their salt can
steal the compute time to do this in university labs, badly secured
The Blaze, Rivest, Diffie, et al paper made some estimates for
raw rc4-40 based on hardware time & cost. Ian Goldberg & David Wagner
came up with highers estimates for the rc4[md5(key+salt)] used in ssl,
because md5 doesn't work easily on the very low end fpga systems that
they were using. The Wagner Goldberg paper is entitled 'Architectural
Considerations for Cryptanalytic hardware'
Chris Kostick wrote:
| > Reading CISCO's online technology briefs for the forthcoming (is there a
| > firm release date ?) IOS 11.2 which includes network level encryption services
| > (DES encryption) (http://www.cisco.com/warp/public/732/Security/ncryp_tc.htm)
| > functionally it's exactly what we need to setup various distinct user groups
| > - however, according to Diffie, Blaze, Rivest et al
| > (http://www.bsa.org/policy/encryption/cryptographers.html)
| > the exportable key length (40 bits) is far too small, even the domestic
| > length (according to them) (56 bits) doesn't cut it.
| This one has always bothered me a little - '40 bits is way too small.' There are
| 1,099,511,627,776 possible combinations of a key. Given today's technology it is
| crackable using brute force methods. But, who is going to do that? A person
| or persons have to have *a lot* of CPU power to crack it in a reasonalble amount
| time unless they get really really lucky. A government can do it fairly
| fast I imagine. Larger corporations like IBM , Microsoft, DEC, Citicorp,
| DOW, Exxon, etc............. can probably supply the horsepower needed. Are
| these people your adversaries? If not, then your risk is not as great as people
| like Diffie, Blaze and Rivest make it out to be.
"It is seldom that liberty of any kind is lost all at once."