From: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
---|---|
To: | Stephen Frost <sfrost(at)snowman(dot)net> |
Cc: | Ryan Lambert <ryan(at)rustprooflabs(dot)com>, Joe Conway <mail(at)joeconway(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Antonin Houska <ah(at)cybertec(dot)at>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, "Moon, Insung" <Moon_Insung_i3(at)lab(dot)ntt(dot)co(dot)jp>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [Proposal] Table-level Transparent Data Encryption (TDE) and Key Management Service (KMS) |
Date: | 2019-07-10 06:45:05 |
Message-ID: | CAD21AoDNKOyhR9WCMuTkWwUuSq+W87nZJD3jQWu0_wWxJf8K6g@mail.gmail.com |
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On Wed, Jul 10, 2019 at 11:06 AM Stephen Frost <sfrost(at)snowman(dot)net> wrote:
>
> Greetings,
>
> * Ryan Lambert (ryan(at)rustprooflabs(dot)com) wrote:
> > > What I think Tomas is getting at here is that we don't write a page only
> > > once.
> >
> > > A nonce of tableoid+pagenum will only be unique the first time we write
> > > out that page. Seems unlikely that we're only going to be writing these
> > > pages once though- what we need is a nonce that's unique for *every
> > > write* of the 8k page, isn't it? As every write of the page is going to
> > > be encrypting something new.
> >
> > > With sufficient randomness, we can at least be more likely to have a
> > > unique nonce for each 8K write. Including the LSN seems like it'd be a
> > > possible alternative.
> >
> > Agreed. I know little of the inner details about the LSN but what I read
> > in [1] sounds encouraging in addition to tableoid + pagenum.
> >
> > [1] https://www.postgresql.org/docs/current/datatype-pg-lsn.html
>
> Yes, but it's still something that we'd have to store somewhere- the
> actual LSN of the page is going to be in the 8K block.
Can we use CBC-ESSIV[1] or XTS[2] instead? IIUC with these modes we
can use table oid and page number for IV or tweak and we don't need to
change them each time to encrypt pages.
[1] https://en.wikipedia.org/wiki/Disk_encryption_theory#Encrypted_salt-sector_initialization_vector_.28ESSIV.29
[2] https://en.wikipedia.org/wiki/Disk_encryption_theory#XEX-based_tweaked-codebook_mode_with_ciphertext_stealing_(XTS)
Regards,
--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
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