Securing Cloud Data with Virtual Private Storage

By Rich

For a couple of weeks I’ve had a tickler on my to do list to write up the concept of virtual private storage, since everyone seems all fascinated with virtualization and clouds these days. Luck for me, Hoff unintentionally gave me a kick in the ass with his post today on EMC’s ATMOS. Not that he mentioned me personally, but I’ve had “baby brain” for a couple of months now and sometimes need a little external motivation to write something up. (I’ve learned that “baby brain” isn’t some sort of lovely obsession with your child, but a deep seated combination of sleep deprivation and continuous distraction).

Virtual Private Storage is a term/concept I started using about six years ago to describe the application of encryption to protect private data in shared storage. It’s a really friggin’ simple concept many of you either already know, or will instantly understand. I didn’t invent the architecture or application, but, as foolish analysts are prone to, coined the term to help describe how it worked. (Not that since then I’ve seen the term used in other contexts, so I’ll be specific in my meaning).

Since then, shared storage is now called “the cloud”, and internal shared storage an “internal private cloud”, while outsourced storage is some variant of “external cloud”, which may be public or private. See how much simpler things get over time?

The concept of Virtual Private Storage is pretty simple, and I like the name since it ties in well with Virtual Private Networks, which are well understood and part of our common lexicon. With a VPN we secure private communications over a public network by encrypting and encapsulating packets. The keys aren’t ever stored in the packets, but on the end nodes.

With Virtual Private Storage we follow the same concept, but with stored data. We encrypt the data before it’s placed into the shared repository, and only those who are authorized for access have the keys. The original idea was that if you had a shared SAN, you could buy a SAN encryption appliance and install it on your side of the connection, protecting all your data before it hits storage. You manage the keys and access, and not even the SAN administrator can peek inside your files. In some cases you can set it up so remote admins can still see and interact with the files, but not see the content (encrypt the file contents, but not the metadata).

A SaaS provider that assigns you an encryption key for your data, then manages that key, is not providing Virtual Private Storage. In VPS, only the external end-nodes which access the data hold the keys. To be more specific, as with a VPN, it’s only private if only you hold your own keys. It isn’t something that’s applicable in all cloud manifestations, but conceptually works well for shared storage (including cloud applications where you’ve separated the data storage from the application layer).

In terms of implementation there are a number of options, depending on exactly what you’re storing. We’ve seen practical examples at the block level (e.g., a bunch of online backup solutions), inline appliances (a weak market now, but they do work well), software (file/folder), and application level.

Again, this is a pretty obvious application, but I like the term because it gets us thinking about properly encrypting our data in shared environments, and ties well with another core technology we all use and love.

And since it’s Monday and I can’t help myself, here’s the obligatory double-entendre analogy. If you decide to… “share your keys” at some sort of… “key party”, with a… “partner”, the… “sanctity” of your relationship can’t be guaranteed and your data is “open”.

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Hi Rich,

Hope all is going well for you.  I’ve been a big fan of your work since I started following you back when I was working at Reconnex.

Couldn’t agree more on the concept of ‘virtual private storage’.  The analogy I like to give is that of online banking, but your use of VPNs may be a more appropriate analogy.  Would love to get your feedback as someone who is respected and authoritative in the security space on a blog post I created for this topic, if you have the time (


By Joel Christner

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