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Date:   Wed, 26 Jan 2022 16:51:29 +0200
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Martin Ross <mross@pobox.com>
Cc:     corbet@lwn.net, dhowells@redhat.com, jejb@linux.ibm.com,
        jmorris@namei.org, keyrings@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-integrity@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org, serge@hallyn.com,
        Yael Tiomkin <yaelt@google.com>,
        Mimi Zohar <zohar@linux.ibm.com>
Subject: Re: [PATCH v4] KEYS: encrypted: Instantiate key with user-provided
 decrypted data
Message-ID: <YfFf8fvsDm8lQJgJ@iki.fi>
References: <CA++MVV3Jse4WZ-zr-SUWQz3Gk_dByU6JduVfUkvQNW+jgm9O4Q@mail.gmail.com>
 <YfFe9+XDPDIdSqF1@iki.fi>
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On Wed, Jan 26, 2022 at 04:47:22PM +0200, Jarkko Sakkinen wrote:
> On Tue, Jan 18, 2022 at 01:26:05PM -0500, Martin Ross wrote:
> > Hi Jarkko,
> > 
> > I have been working with Yael on this project so I thought I might add
> > a bit of background here around the use case that this series of
> > patches is trying to address.
> > 
> > At a high level we are trying to provide users of encryption that have
> > key management hierarchies a better tradeoff between security and
> > availability.  For available and performance reasons master keys often
> > need to be released (or derived/wrapped keys created) outside of a KMS
> > to clients (which may in turn further wrap those keys in a series of
> > levels).  What we are trying to do is provide a mechanism where the
> > wrapping/unwrapping of these keys is not dependent on a remote call at
> > runtime.  e.g.  To unwrap a key if you are using AWS KMS or Google
> > Service you need to make an RPC.  In practice to defend against
> > availability or performance issues, designers end up building their
> > own kms and effectively encrypting everything with a DEK.  The DEK
> > encrypts same set as the master key thereby eliminating the security
> > benefit of keeping the master key segregated in the first place.

Mainly this part (would be enough to explain why it is there).

BR, Jarkko