Actually, if y < 160, there's no guarantee that you'll get more than 1 file with the same CHK. Actually, there never is, but it becomes much less likely with y < 160, as some CHKs will have to be unused. However, since Freenet rounds file sizes less than 8192 bits up to that in the CHK file-size field, it's not exactly relevant.
And actually, (2^N)/(2^160) is a good estimate for the number of N-bit files with a given CHK; getting larger than N is not a problem, getting larger than 2^N (the total number of different files with N bits) is the impossibility, but obviously will never happen. -----Original Message----- From: Lorrin Nelson <[EMAIL PROTECTED]> Sent: Sep 10, 2003 9:47 PM To: Discussion of development issues <[EMAIL PROTECTED]> Subject: Re: [freenet-dev] CHK collision and denial of service Yeah, I'm not sure this logic is getting anywhere. Lets say I want to block a particular y bit file (y < 160) with CHK x. If you start trying to find a file with CHK x by looking at all possible files, then of course you'll find the file in just 2^y tries, since you'll have stumbled across the actual file! But that's no use to use, since you need a _different_ file than the one you're trying to block. So you've gotta keep looking, and that'll probably take 2^159 tries as was said earlier. I just made all this up so maybe I'm wrong, but it makes sense to me. :-) _______________________________________________ Devl mailing list [EMAIL PROTECTED] http://dodo.freenetproject.org/cgi-bin/mailman/listinfo/devl
