Intentionally I left the problem generic. Is the probability near to 1? You can suppose that A is 500 bytes long, that the server knows the hash value of A (but not A), that it searchs only strings of this length with the same hash value, that it found such a string B, that the hash function is the concatenation of the rolling hash of rsync with md4.
You can also suppose that A and B are 4 TB long and the hash sha1. Rodrigo. Tony Abernethy <[email protected]> wrote: > INSUFFICIENT DATA > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of > [email protected] > Sent: Tuesday, September 17, 2013 10:28 AM > To: [email protected] > Subject: Re: cvsync, rsync > > Marc Espie <[email protected]> wrote: > > > > You have strings A and B, and you know only that hash(A)=hash(B): what > > > is the probability that A=B? 2^-160? > > > > No, that's never the problem. > > > > You have a *given* string A, and another string B. > > O.K. You have string A in the client with hash(A)=n. You find string > B in the server also with hash(B)=n. What is the probability that > A=B? > > Rodrigo.
