Re: What is md5sum?
From: Bill Unruh (unruh_at_string.physics.ubc.ca)
Date: Wed, 30 Jun 2004 15:41:43 +0000 (UTC)
Carlos Moreno <email@example.com> writes:
]P.T. Breuer wrote:
]>>When did I say that the rest of the universe is wrong?? The
]> When you say that md5sum does not identify a files contents uniquely.
]Actually, you are the one that says that that means the rest of
]the universe is wrong.
]I *know* for a fact that md5sum does not guarantee that a file
]is unique. You still have not proven the opposite. You say
There are two separate questions. Is it mathematically possible that there
exist-- in the mathematical sense-- two files with the same MD5sum. Yes.
Is it possible that there exist in the world as we know it and experience
it two files with the same md5sum? He and I answer no.
IF md5 were shown to be cryptographically weak, I would change my answer,
because in that case human ingenuity could create them. But transfer by ftp
]that MD5 *is* unique to a file (because of the very nature of
]the energy of the solar system or something like that). Why
]don't *you* prove that?? Using your very logic, if you say
]that MD5 is unique to every file, then show me, show me *ALL*
]the files that have ever existed and *will ever* exist, and
]their MD5s -- if they're all different, then you have proved
]your case and I will believe you and I will admit that I am
]mistaken. But you *have to prove it*, and not ask me to show
]you a counter-example.
Actually you were the one who started this with a claim that I was WRONG to
state to a user asking about md5 that the same md5sum meant that his file
was the same as the original.
]Your statement seems much more definitive than mine -- I'm
]simply saying that it is possible for something to happen
No, for you are using the word possible in a sense that noone else ever
uses it in real life (rather than in mathematics). To tell a user that this
is possible is simply to lie and decieve for to state that it is possible
in common useage means it is something he should be concerned about at some
]even if I haven't seen it (or will see it) happen. You are
]saying that there are not and there can not be two different
]files with the same MD5 -- *prove it*. And you know, I
]will not accept any B.S. with philosophical blahblahs about
]the nature of the universe. I only believe in what I see;
No you do not. That is just the issue. You are asking that user to be
concerned about something they will never see.
]HEY!! What do you mean convinced that the mechanism was capable??
]We're not talking abstract philosophical B.S. here!! You should
Yes, you were the one who started this by talking abstract philosophical BS.