Re: [Proposal] Table-level Transparent Data Encryption (TDE) and Key Management Service (KMS)

On 7/8/19 6:04 PM, Stephen Frost wrote:
> * Bruce Momjian (bruce(at)momjian(dot)us) wrote:
>> Uh, well, renaming the user was a big problem, but that is the only case
>> I can think of. I don't see that as an issue for block or WAL sequence
>> numbers. If we want to use a different nonce, we have to find a way to
>> store it or look it up efficiently. Considering the nonce size, I don't
>> see how that is possible.
>
> No, this also meant that, as an attacker, I *knew* the salt ahead of
> time and therefore could build rainbow tables specifically for that
> salt. I could also use those *same* tables for any system where that
> user had an account, even if they used different passwords on different
> systems...
>
> I appreciate that *some* of this might not be completely relevant for
> the way a nonce is used in cryptography, but I'd be very surprised to
> have a cryptographer tell me that a deterministic nonce didn't have
> similar issues or didn't reduce the value of the nonce significantly.

I have worked side by side on projects with bona fide cryptographers and
I can assure you that they recommended random nonces. Granted, that was
in the early 2000s, but I don't think "modern cryptography" has changed
that any more than "web scale" has made Postgres irrelevant in the
intervening years.

Related links:

https://defuse.ca/cbcmodeiv.htm
https://www.cryptofails.com/post/70059609995/crypto-noobs-1-initialization-vectors

Joe

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