From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Fri, 25 Nov 2005 01:13:54 GMT
Subject: Re: Problem merging
Message-ID: <Pine.LNX.4.63.0511250208500.28437@wbgn013.biozentrum.uni-wuerzburg.de>
In-Reply-To: <D8B7EF65-9D0C-4706-B248-4B7C118C16BF@hawaga.org.uk>

Hi,

On Thu, 24 Nov 2005, Ben Clifford wrote:

> On 24 Nov 2005, at 00:49, Johannes Schindelin wrote:
> 
> > I think nobody is. Since there are infinitely many files having the same
> > SHA1 (pigeon-hole principle),
> 
> hmm... pigeon-hole principle is just that there exists two files that 
> have the same SHA-1 as each other... doesn't say anything about *all* 
> SHA-1s, though?

Okay, the second part of the truth is: It would be a lousy cryptographic 
hash (which it isn't), if the SHA1s were not uniformly distributed over 
the possible data.

You actually can be reasonably sure that given the SHA1s of all messages 
of length up to N (N being an integer at least the number of bits of the 
hash, i.e. 160 for SHA1), the counts of the different SHA1s should be 
equal.

Ciao,
Dscho