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Posted by Rik Wasmus on 11/26/07 04:03
On Mon, 26 Nov 2007 04:22:41 +0100, Kailash Nadh <kailash.nadh@gmail.com>
wrote:
> On Nov 23, 7:13 pm, Toby A Inkster <usenet200...@tobyinkster.co.uk>
> wrote:
>> Rik Wasmus wrote:
>> > You can't decrypt/decode it though (well, at least not practically).
>>
>> Well, you can't at all, because for any given MD5 hash, there are
>> infinite
>> possible inputs which could have generated it. So even if you manage to
>> find an input which produces that value as its output (which is more or
>> less an enormous brute-force search), you can't be sure that it's the
>> same
>> as the original input.
> Toby, I think you are mistaken.
> In theory, every md5 hash is unique. An md5 hash is bound to a single
> unique input. If a brute-force matches a has, THAT is the original
> input.
No, Toby is right: different input can generate the same output (if not,
we would have found a great ZIP functionality, didn't we? If we can md5 a
file, and every md5 is unique yet limited to a certain length, you could
put all books into one file, and md5 it. If a md5 is unique, it is
reversable.). Brute force cracking involves guessing at original input
length & propability of input. It can be done (with 'propabilities of
input', it's not something hackers would like to spend their CPU cycles on
though.
--
Rik Wasmus
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