Time to crack DES? Is it a task suitable for a script kiddie yet?

MatthewMartin picture MatthewMartin · Jul 31, 2009 · Viewed 10.6k times · Source

Already understanding that AES is the encryption method of choice, should existing code that uses DES be re-written if the likely threat is on the level of script kiddies? (e.g. pkzip passwords can be cracked with free utilities by non-computer professionals, so is DES like that?) A quick google search seems to imply that even deprecated DES still requires a super computer and large quantity of time--or have times changed?

In particular, this CAPTCHA library uses DES to encrypt the challenge string which is sent to the user in viewstate.

Answer

David picture David · Jul 31, 2009

DES is broken so far as storing sensitive data, and so I would certainly not use it in anything new, and would replace it in anything used for long term storage of any information of interest (data that someone would have a profit for national security interest in stealing).

At the moment a DES message can be broken by brute force in a couple of days (or less) using under $100,000 worth of custom hardware.

But there are some key factors in that:

The hardware is custom - the chips used to quickly brute a DES key are not the general purpose processor you'd find in a PC. That being said there is probably room today for using a cluster of Playstation 3s or current generation graphics cards with a GPGPU to crack a DES message in a reasonable amount of time, perhaps bringing down the cost to maybe $15,000.

The other factor is time - a DES message can be cracked in a day, but if your CAPTCHA library has a timestamp that specifies a 30 minute timeout for any given CAPTCHA response, it would still be effective (you could scale up your hardware, but then you're talking millions).

Overall I'd say that for non-long term storage, DES is still secure against "script kiddies".