On Mon, Dec 29, 2003 at 06:12:40PM +0000, danilo ([EMAIL PROTECTED]) wrote: > md5 is used over internet to ensure that the files you have downloaded are > what they are supposed to be. i.e. no one have modified them.
> Anytime a bit is changed, md5 checksum changes too. That is correct, but by itself md5 would not be very useful in this kind of application: it is easy to recompute the checksum after changing something in the image, and write the new checksum matching the altered image to the new file as well. It would be enough to discourage non-computer-savvy image manipulators, but certainly not for legal purposes, IMHO. For that I'd want some public key cryptography algorithm with secret key on chip in the camera and public key available to the software. The description in www.canoneos.com does not tell much, however the fact that the kit includes a dedicated IC card suggests it is using something more complicated than md5. Note that if the thing is implemented properly it could not be forged any easier even if all details of the implementation (except the secret key of course) were made public, and that would increase its trustworthiness thousandfold in the eyes of people who know about these things. -- Tapani Tarvainen * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
