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From <>
Subject RE: Lucene Index Encryption
Date Fri, 08 May 2009 19:02:55 GMT
You are correct, other vulnerabilities will of course be the Swap file,
which is much easier to dump than the memory contents, since it may
persist even when the process dies or the machine is turned off, and of
course a process dump or snapshot file.

In either case, those cracks would be on a system that generally has
access to the data while it is running. Since the same cracks would be
available in the swap or dump file say when an SQL table were in memory
we would have the same issue.

The reality is that the data will need to be decrypted in RAM memory at
sometime in its lifetime whether it is from the Lucene index, or the
original source like and SQL table or a decrypted PDF file. 

However, if the file or the computer is stolen, an encrypted index would
be useless because of the encryption would presumably match that of the
original source.

Other system tools outside of the scope of this discussion would need to
wipe the swap file of secure content when the process dies off the hard


-----Original Message-----
From: patrick o'leary [] 
Sent: Friday, May 08, 2009 2:34 PM
Subject: Re: Lucene Index Encryption

There will always be levels of where data will be insecurely available.
notably within the memory of an application once it's running. Unless
want to go down the path of encrypting and decrypting each and every
At which point you loose dictionary functionality and well any useful

If you run a system where your security concern is for persistent data
storage, e.g. disk, backup's, off lease returns, repairs etc.. and not
volatile storage, one method might be to store the lucene index in a
encrypted archive, file system or a hardware device, and use something
Dave Spencers idea of converting an FSDirectory into a RAMDirectory

Once it's in volatile memory, it's obviously possible with someone who
what they're doing, but a hell of a lot harder to penetrate, when the
process dies the unencrypted data is gone (as long as you're using
appropriate RAM)

On Fri, May 8, 2009 at 1:27 PM, Karl Wettin <>

> I might be missing something here, but why not just store the index on
> cryptographic virtual file system?
>     karl
> 8 maj 2009 kl. 19.09 skrev <>
> >:
>> Michael,
>> Thanks for the comments they are very insightful.
>> I hadn't thought about the Random Access issues until you brought it
>> This makes the project a little tougher, but not impossible.
>> I was searching last night and there have been a couple of papers
>> written on the topic of Encrypted Random Access files at MIT.
>> I haven't finished reading all of them yet, but they suggest ways of
>> solving the Encryption problems for Random Access Files.
>> I am going to spend a few day looking at the various papers before I
>> waste your time discussing this any further.
>>  (Presumably performance will suffer perhaps substantially since
>>> search will need to decrypt on the fly...).
>> Yes, I imagine that there will be a performance hit, this will add
>> significant overhead to every byte that Lucene accesses.
>> However, in some applications the price of having unsecure data is
>> unacceptable, when secure data is published to a laptop for use
>> In this case, the additional time needed to access the index would be
>> acceptable.
>> Examples: Military, Medical, and Financial information.
>> Thanks,
>> Peter
>> Subject:
>> Re: Lucene Index Encryption
>> <>
>> Actions...
>> From:
>> Michael McCandless (
>> Date:
>> May 5, 2009 1:22:00 am
>> List:
>> Would you encrypt at the file level?  Ie, the encryption would live
>> "under" a RandomAccessFile (RAF) and otherwise feel "normal" to
>> Lucene?
>> (I think I remember others exploring encryption at the individual
>> level, which is interesting but does leak information in that you can
>> see individual terms & their frequencies).
>> Lucene needs to be able to ask a RAF opened for writing what it's
>> current "position" is during indexing, which it then stores away, and
>> later during searching it needs to ask a RAF opened for reading to
>> seek back to that position so it can read bytes from there.  Would
>> encryption APIs allow this?
>> If this is possible then couldn't one make a Directory impl that
>> all encryption/decryption "under the hood"?
>> (Presumably performance will suffer perhaps substantially since every
>> search will need to decrypt on the fly...).
>> Mike
>> On Mon, May 4, 2009 at 6:29 PM,  <> wrote:
>> I hope to make this a discussion rather than a request for a feature.
>> In the database world, secure data is always encrypted in the
>> Since I am interested in storing data from a database in the index,
>> times I want to encrypt the index when the file is one disk.
>> Currently data stored in the Lucene Index is easily accessible to any
>> program that wants to access it. You cannot store sensitive data in
>> index without the fear that it will be readable by all the people
>> have access to the system.
>> There are two other posts in the mailing list that ask a question
>> Lucene Index Encryption. In both cases, I think that the conservation
>> was dropped or the feature put off.
>> Basically, I am asking for comments on the topic. I might consider
>> coding the feature, but I would only do it if I am sure that the
>> would be useful and accepted back into the core codebase of Lucene.
>> The Sun javax.crypto package is available in the JDK 1.4 so using
>> package could be possible way of providing an encrypted file.
>> The other option is Bouncy Castle, which is now being used in the
>> and Tika projects.
>> In any case, because the normal Lucene Index implementation would not
>> use an encrypted index, all references to Security classes should
>> dynamically with the "Class.forName()" method if they were not part
of a
>> standard JRE, to guarantee no additional requirements are placed on
>> people currently using the Lucene libraries.
>> Then there is the issue of what to use as the Encryption Key, and how
>> allow access to the Index files from the various programs that may
>> to get to the data. The Encryption Key needs to external from any
>> program that accesses the Index, because with Java, if the key were
>> stored in the code, it would be easily found with a simple decompile
>> the Java class.
>> I don't have answers to the questions, but basically I am requesting
>> comments on the topic.
>> I imagine that if I put Encryption and Decryption at the I/O level,
>> immediately before a segment was written or immediately after a
>> was read, that I would minimize the overall impact of the Lucene
>> Library.
>> Another area to address is Remote Searching. The Remote Interface
>> need extensions that allow for Encrypted Remote files as well as
>> Encrypted communication between the machines.
>> However, I am not sure of these assumptions. I don't know how many
>> places the segments are read and written. I really do not know how to
>> this currently, but would be willing to give it a try it there was
>> enough interest shown in the topic.
>> Peter
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