Talk:40-bit encryption

Feel free to correct me if I'm wrong, but isn't DES in reality a 40-bit encryption standard? I know it actually has 56 bits, but my understanding was that for various reasons it really only offered 40 bits of encryption, and so is generally referred to as a 40 bit encryption method? Even the version of this page prior to my edit cited Deep Crack as being able to break 40 bit encryption rediculously fast (though I think it was very wrong on the time taken), and again, my understanding was that Deep Crack was built for DES and nothing else, so why was it referred to in an article on 40 bit encryption?

Deep Crack is the only dedicated brute force machine built for key search that we have the details about; I think the reason the machine is mentioned is that, when considering a key-size, it's useful to consider how well Deep Crack would perform given keys of that length. The machine was designed to be able attack up to the full 56 bits of DES. As a standard, DES accepts a 64-bit key; however, 8 bits are discarded as "parity bits" (well, that's the explanation given, anyway!), leaving 56 bits, the number usually quoted. Have a look at the references at the end of DES if you'd like to check up on this. There are theoretical attacks on DES that take an amount of time equivalent to brute forcing around 39-43 bits, but these aren't practical in any real-world-security sense. — Matt 13:50, 17 Sep 2004 (UTC)