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From John Haxby <>
Subject Re: Encryption
Date Sat, 06 May 2006 20:51:04 GMT
George Washington wrote:
> Is it possible to reconstruct a complete source document from the data 
> stored in the index, even if the fields are only indexed but not 
> stored? Because if the answer is "yes" there is no point in 
> encrypting, unless the index itself can be encrypted. Is it feasible 
> to encrypt the index?

As Otis said, no, in general it's not possible to reconstruct the 
document, but that might not be needed to discover interesting thing 
about the documents.  For example, it's interesting to know if lots of 
documents contain the word "zimbra" or the words "eliminate" and 
"competition" -- smile -- near each other.   I'm sure you can dream up 
your own examples.

If your documents need to be encrypted to protect them, then I would say 
that your index does as well.   Although you can't reconstruct the 
original document you can certainly find out all kinds of interesting 
things even just by searching for phrases, let alone looking at what 
terms were indexesd.

As Otis also suggested, your best bet is going to be to use an encrypted 
file system; both Linux and Windows offer this capability.   Of course, 
and I presume you've already done this for the douments, you're going to 
have to worry about the safety of the key used to encrypt the file 
system and all the other associated security issues.

jch (I wouldn't be paranoid if they weren't out to get me)

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