[Xapian-discuss] Encrypted Database Files

[Sam Liddicott]

Jim Lynch wrote:

> I don't know if there is a way to turn off positional information in 
> the database or not, however if there isn't then a person could 
> conceivably rebuild the message.  If stemming is turned on, the words 
> might be a little strange, e. g. no plurals, no -ed or -ing, etc. but 
> the gist of the message could be recognizable.  I doubt there is a 
> modern search engine that doesn't store positional information.
> As James said earlier, I've never tried it, but I think it is possible.
> It would be a lot of work and it would slow searching and indexing 
> down a bunch but you could modify the code to store encoded blocks of 
> data since the source is available to you.  In fact, you would only 
> need to encode the positional data, not the terms themselves.


The sort of data that is worth incrypting is almost by definition the 
sort of data worth going to this much trouble to recover.

AFAIRC this actually happened about 20 years ago, some lowly students 
who were not allowed copies of some of the dead-sea scrolls were allowed 
an index of all scroll fragments (or words on fragmens) and where they 
occurred in the main scroll; from this (using a mac computer no less) 
the produced the original scroll.

BBC reported on this at the time.

Sam


>
> Jim.
>
> David Blewett wrote:
>
>> Hi all:
>>
>> I'm considering using Xapian to index email messages in an IMAP 
>> server I'm writing. Is it possible to encrypt the databases stored on 
>> disk, so that someone cannot recover their contents?
>>
>> What I would like to do is when a message is received, send it 
>> through Xapian to be indexed. Then encrypt the contents and store it. 
>> When I run a search through Xapian, all I need is some sort of ID so 
>> I can retrieve the message and decrypt it. I don't want someone to be 
>> able to use the Xapian database to reconstruct the messages indexed. 
>> Is this possible?  If not, is there another indexing engine that can? 
>> Thanks!
>>
>> David
>>
>>
>>
>>
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