[dm-crypt] dm-crypt Digest, Vol 27, Issue 2

Shardis shardis at charter.net
Thu Sep 1 20:22:02 CEST 2011

Agreed that sensitive data doesn't belong in the cloud. How could it when the cloud by definition has to have access to everything to decrypt/encrypt? That's just added exposure for no real gain other than saving some relatively cheap cycles.

If you're having to manage crypto at all - I guess I wasn't saying that well, as I take the additional costs you mentioned as a given.

I'd also add to that list the sheer amount of knowledge and education that's basically required and encompasses all of what you mentioned. Maybe a bit dodgy of me to just lump all of that together, but you either have to know it, have employees that know it, or hire it. All of those are expensive in both time and money.

I'm sure there are others too. I'll go back to lurking, touch screen typing is getting too frustrating and you're articulating everything more clearly than I can anyway. :-) 

Arno Wagner <arno at wagner.name> wrote:

>On Thu, Sep 01, 2011 at 10:58:17AM -0500, Shardis wrote:
>> Personally, I tend to find that the only sane technical reason not to
>> encrypt anything considered sensitive these days is CPU cycle cost.
>I am not arguing that. I am aguing that "sensitive" data
>has no place in a non-private cloud in the first place,
>and hence the discussion whether to encrypt sensitive 
>data in a non-private cloud or not does not apply.
>I am also aguing that for non-sensitive data, encryption
>may cause more problems than it solves, see below.
>> For the vast, VAST majority of use cases the cost of CPU cycles is almost
>> inconsequential when compared to the cost of any other knowledge,
>> hardware, software, management and support that would be needed in any
>> case.
>> While I'm not intimately familiar with broadcast media uses - I would
>> strongly suspect that this would be the case even there.
>> Or maybe I just don't have a lively enough imagination. I do work
>> operations in a data center with at least a few petabytes on hand though.
>> Why would you ever NOT want to encrypt in house?
>Keeping in mind that the topic is block-layer
>encryption, you have added cost for:
>- CPU and power
>- key management
>- risk of key loss (and data loss as a consequence)
>- encryption software management
>- increased complexity
>- more difficult data recovery and problem detection
>- analysis of on-disk data requires keys and working decryption 
>- problems when law enforcement comes with a warrant
>I am sure there are a few others. 
>> Yaron Sheffer <yaronf at gmx.com> wrote:
>> >Hi Arno,
>> >
>> >Encryption of data-at-rest in the public cloud is not "pointless", it is 
>> >yet another layer of security. Just as people encrypt their laptops even 
>> >though they are password protected.
>> >
>> >The cloud provider does not have access to "everything", certainly not 
>> >when we're talking about data at rest, where the keys may have come and 
>> >gone months ago but the data is still there. Moreover, the cloud 
>> >provider is not the only or the most important threat. By the way, I am 
>> >not claiming that the permission system is broken.
>> >
>> >Attacks on encrypted data are no harder or more expensive in the cloud 
>> >than on physical disks. If you parallelize things, your throughput is 
>> >limited by the disks physical access, just as for "real" disks.
>> >
>> >This is a solution for a very real problem. But I don't want to go 
>> >commercial again...
>> >
>> >Thanks,
>> >     Yaron
>> >
>> >On 09/01/2011 02:38 PM, dm-crypt-request at saout.de wrote:
>> >
>> >
>> >Message: 2
>> >Date: Thu, 1 Sep 2011 13:27:24 +0200
>> >From: Arno Wagner<arno at wagner.name>
>> >To: dm-crypt at saout.de
>> >Subject: Re: [dm-crypt] Blog post on FDE and integrity protection
>> >Message-ID:<20110901112724.GB4617 at tansi.org>
>> >Content-Type: text/plain; charset=us-ascii
>> >
>> >Disk encryption in a non-private cloud is pretty pointless.
>> >The cloud provider can access everything. An attacker should
>> >reliably be kept from accessing your storage, otherwise you are
>> >screwed anyways. I know, people are doing this, but they are
>> >kidding themselves.
>> >
>> >For your EBS scenario, true, block-level encryption
>> >can be done, but it is irrelevant. Encryption is not the
>> >right way to fix a broken cloud permission system. Critical
>> >encrypted data should never be decrypted in the cloud. It
>> >is just not secure. On the other hand, attacks that
>> >manipulate encrypted images are not relevant for lower
>> >security requirements, as they are very hard (expensive)
>> >to do.
>> >
>> >This makes integtity protection of encrypted data in the cloud
>> >a complete non-issue. This is a solution without a problem.
>> >
>> >Arno
>> >
>> >
>> >
>> >
>> >On Thu, Sep 01, 2011 at 01:51:38PM +0300, Yaron Sheffer wrote:
>> >
>> >>> Hi Arno,
>> >>>
>> >>> Thank you for reviewing my post. Please see my comments below.
>> >>>
>> >>> Thanks,
>> >>>      Yaron
>> >>>
>> >>>> Message: 3
>> >>>> Date: Wed, 31 Aug 2011 23:29:40 +0200
>> >>>> From: Arno Wagner<arno at wagner.name>
>> >>>> To: dm-crypt at saout.de
>> >>>> Subject: Re: [dm-crypt] Blog post on FDE and integrity protection
>> >>>> Message-ID:<20110831212940.GB25013 at tansi.org>
>> >>>> Content-Type: text/plain; charset=us-ascii
>> >>>>
>> >>>>
>> >>>> Commercial, for sure. It combines fragments from well-known
>> >>>> facts and marketing speech. And it has not understood the
>> >>>> problem, advertizing for SAN/cloud services, where storage is
>> >>>> not block-based but file-based.
>> >>> The most commonly used public cloud is Amazon WS. This cloud offers
>> >>> two storage possibilities, S3 which is object ("file") storage, and
>> >>> EBS which is block storage, and is exposed to the application as a
>> >>> disk volume. The post is about EBS, sorry if that wasn't clear.
>> >>>> I should also note to anyone contemplating "solution" 3
>> >>>> that RAID1 does not read both devices on read access,
>> >>>> and inconsistencies will only show up if you or your
>> >>>> distro does RAID consistency checks.
>> >>> This is correct, thanks.
>> >>>> And of course the whole article does not apply to the
>> >>>> SAN/cloud setting in the first place, as the attack
>> >>>> scenario is for an unmapped encrypted filesystem and
>> >>>> an attacker getting write access to that, i.e. the
>> >>>> encrypted raw (block) view needs to be exported to
>> >>>> the attacker. I do not see how that would be done in the
>> >>>> SAN/Cloud setting. These do their own filesystem
>> >>>> and block encryption must be done below the FS layer,
>> >>>> there is no way around that.
>> >>> The attack scenario is for someone who has access (possibly limited
>> >>> access) to your cloud account to detach your EBS volume from its
>> >>> current virtual server, attach it to a different server, and then
>> >>> modify the (encrypted) storage. This is all completely doable and
>> >>> actually standard procedure on AWS.
>> >>>> Arno
>> >>>>
>> >>>>
>> >>>>
>> >>>> On Wed, Aug 31, 2011 at 04:25:51PM +0200, Heinz Diehl wrote:
>> >>>>> On 31.08.2011, Yaron Sheffer wrote:
>> >>>>>
>> >_______________________________________________
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>Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno at wagner.name 
>GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
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