Re: storing an explicit nonce

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>, Andres Freund <andres(at)anarazel(dot)de>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Tom Kincaid <tomjohnkincaid(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com>
Subject: Re: storing an explicit nonce
Date: 2021-05-26 20:40:48
Message-ID: 20210526204048.GW3048@momjian.us
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On Wed, May 26, 2021 at 01:56:38PM -0400, Robert Haas wrote:
> However, I believe that if we store the nonce in the page explicitly,
> as proposed here, rather trying to derive it from the LSN, then we
> don't need to worry about this kind of masking, which I think is
> better from both a security perspective and a performance perspective.

You are saying that by using a non-LSN nonce, you can write out the page
with a new nonce, but the same LSN, and also discard the page during
crash recovery and use the WAL copy?

I am confused why checksums, which are widely used, acceptably require
wal_log_hints, but there is concern that file encryption, which is
heavier, cannot acceptably require wal_log_hints. I must be missing
something.

Why can't checksums also throw away hint bit changes like you want to do
for file encryption and not require wal_log_hints?

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

If only the physical world exists, free will is an illusion.

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