Re: Transparent Data Encryption (TDE) and encrypted files

On Thu, Oct 10, 2019 at 10:40:37AM -0400, Stephen Frost wrote:
> > Some people ask for indexable encrypted columns, but I tend to explain to
> > them how impractical and inefficient that is. You can support hash indexes
> > if you don't salt the encrypted data, but that greatly weakens the
> > encryption by allowing attackers to use dictionary attacks and other brute
> > force techniques efficiently. And you can't support b-tree > and < without
> > very complex encryption schemes (
> > https://en.wikipedia.org/wiki/Homomorphic_encryption).
>
> I'm not sure why you wouldn't salt the hash..? That's pretty important,
> imv, and, of course, you have to store the salt but that shouldn't be
> that big of a deal, I wouldn't think. Agreed that you can't support
> b-tree (even with complex encryption schemes..., I've read some papers
> about how just </> is enough to be able to glean a good bit of info
> from, not super relevant to the overall discussion here so I won't go
> hunt them down right now, but if there's interest, I can try to do so).

Yes. you can add salt to the value you store in the hash index, but when
you are looking for a matching value, how do you know what salt to use
to find it in the index?

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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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