On 17 Apr 2002, David Bolen <[EMAIL PROTECTED]> wrote: > Martin Pool [[EMAIL PROTECTED]] writes: > > > To put it in simple language, the probability of an file transmission > > error being undetected by MD4 message digest is believed to be > > approximately one in one thousand million million million million > > million million. > > I think that's one duodecillion :-) > > As a cryptographic message-digest hash, MD4 (and MD5) is intended as > having 2^128 operations necessary to crack a specific digest (find the > original source), but probably only on the order of 2^64 operations to > find two messages that have the same digest. But even that isn't a > direct translation to the probability that two random input strings > might hash to the same value.
I suppose what we're trying to calculate is the probability that for a given file, a set of random errors produce a file with the same digest. I *think* that means the birthday paradox in fact does not apply, and so the answer is closer to 2^128, not 2^64. The birthday paradox probably does apply when searching for matching blocks. -- Martin -- To unsubscribe or change options: http://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.tuxedo.org/~esr/faqs/smart-questions.html
