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AJvYcCU/ktvMb/3LqLIpwRFy9wZlHvg2v55Z9BF90Y9qcC5AQp5OlDayXyJAlQKIfQABBTqR5Dtxxsrt+uVRseG0CDEpPh1JLWoCNv7P8yqE X-Gm-Message-State: AOJu0YzIbE7Im+XkS70zQMlgyXatW4ewI66qx6zodoUZIK3R/ANBipdb rdZjJUYQ/ItZbMjRvdZU2Xx4vJi33WbPVmwvMCptbqxUSpvX6sy8qEPQS3wCLpGT9GD12Y8Sfvp rINM5kk3k3mCowi2vmwyc6H0orooMV7V5+B/V1Q== X-Received: by 2002:a17:90a:b38e:b0:2b5:6f9b:a7b with SMTP id 98e67ed59e1d1-2b6cc759192mr10553268a91.15.1715702474405; Tue, 14 May 2024 09:01:14 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20240503221634.44274-1-ignat@cloudflare.com> <3bfcacf38d4f5ab5c8008f2d7df539012940222e.camel@HansenPartnership.com> In-Reply-To: From: Ignat Korchagin Date: Tue, 14 May 2024 17:01:03 +0100 Message-ID: Subject: Re: [RFC PATCH 0/2] TPM derived keys To: James Bottomley Cc: Jarkko Sakkinen , Mimi Zohar , David Howells , Paul Moore , James Morris , serge@hallyn.com, linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@cloudflare.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, May 14, 2024 at 4:54=E2=80=AFPM James Bottomley wrote: > > On Tue, 2024-05-14 at 16:38 +0100, Ignat Korchagin wrote: > > On Tue, May 14, 2024 at 4:30=E2=80=AFPM James Bottomley > > wrote: > > > > > > On Tue, 2024-05-14 at 14:11 +0100, Ignat Korchagin wrote: > > > > * if someone steals one of the disks - we don't want them to > > > > see it has encrypted data (no LUKS header) > > > > > > What is the use case that makes this important? In usual operation > > > over the network, the fact that we're setting up encryption is > > > easily identifiable to any packet sniffer (DHE key exchanges are > > > fairly easy to fingerprint), but security relies on the fact that > > > even knowing that we're setting up encryption, the attacker can't > > > gain access to it. The fact that we are setting up encryption > > > isn't seen as a useful thing to conceal, so why is it important for > > > your encrypted disk use case? > > > > In some "jurisdictions" authorities can demand that you decrypt the > > data for them for "reasons". On the other hand if they can't prove > > there is a ciphertext in the first place - it makes their case > > harder. > > Well, this isn't necessarily a good assumption: the way to detect an > encrypted disk is to look at the entropy of the device blocks. If the > disk is encrypted, the entropy will be pretty much maximal unlike every > other use case. The other thing is that if the authorities have your What if the disk is filled with random data? Would it not be at maximal ent= ropy? > TPM, they already have access to the disk in this derived key scenario. I'm thinking more of a datacenter scenario here - it is much easier to "steal" a disk rather than a server from a datacenter. So it is possible that someone has the disk but no access to the TPM. > If *you* still have access to your TPM, you can update the storage seed > to shred the data. The point here is not if I was able to shred the data or not, but the fact I have something encrypted. Even if I shred the key I would be considered "uncooperative and refusing to provide the key" vs "I don't have anything encrypted in the first place". > James >