Cynic wrote:
> On Fri, 9 May 2008 18:09:24 -0700 (PDT), Jethro
> wrote:
>
>> Does anyone know of any software which will allow a person to create
>> a hash of a file (say a text document) with a specific key. The idea
>> being that the hash can be published with the document, but the
>> original author can prove it was he who signed it (implying it was he
>> who wrote it).
>
> PGP - download for free.
>
>> Would such a system be admissable in a UK court as proof of prior
>> authorship ?
>
> Yes, I should think that it would be admissable, though it may be
> necessary to hire a suitable expert witness to explain to the court
> how it works and how effective it is.
>
> All it proves of course is that you had the document in your
> possession at some time. It does not prove that you are the author of
> the document. Anyone could take the document, remove your digital
> signature, append their own and republish it.
But surely that's the whole point of checksum verification that the OP was
asking about.
If someone did change a part of the document - even a digital signature -
that would instantly indicate alteration or tampering as the acompanying
code would be different. It wouldn't indicate what exactly had been changed,
but it would show that a change had been made.
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