Disk encryption: not just for paranoids

Many companies are beginning to do something that years ago would have been thought of as overkill: encrypting data while it is sitting on the array. This article will help you decide if this is something your company should do.

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As direct-attached storage (DAS) moves to storage area networks (SANs), a question asked more often of storage administrators these days is: "How safe is our data?"

The question is being asked for a couple of reasons. First, attaching storage to networks introduces security vulnerabilities that didn't exist in the DAS era. And companies are increasingly facing regulations requiring that they take extra steps to keep sensitive customer information private.

The risk associated with sending backup data over an unprotected IP network is obvious. But even an isolated SAN is vulnerable to attack. Many switches, host bus adapters (HBAs) and other fabric elements use management console interfaces that rely on out-of-band connections that are only minimally protected.

"The management interfaces are the first security vulnerability in a SAN fabric that people should look at," says Nancy Marrone-Hurley, a senior analyst with the Enterprise Storage Group (ESG) in Portland, OR. "But there are many other potential problems that most storage managers haven't even begun to think about."

These security concerns are leading a growing number of storage administrators to embrace an idea that not long ago would have qualified as a symptom of paranoid overkill: encrypting data not only as it traverses a storage network, but also as it sits on disk and tape arrays. No doubt the idea makes some sense. If you've encrypted all your critical data, hackers would be prevented from reading it, even if they were able to worm their way into your storage network. But it's not quite as simple as all that--there are trade-offs.

Bringing Encryption tools compared

Different ways to encrypt data
There are many ways to encrypt data for privacy protection as it moves over a storage network and as it sits on a storage device. Here's a rundown of the different approaches:
Application-based encryption. Various applications permit encryption of the data they create or process. Most automated backup applications allow administrators to opt to encrypt data as it's moved off of primary storage, passed through a network and stored on tape or other backup devices. A drawback is that because this type of encryption is usually implemented in software, performance can be slow. Also, if you're running many different types of applications, each may encrypt data and manage encryption keys differently, making administration difficult. As a result, many organizations pass on this encryption option. Mark Bradley, Computer Associates' technology strategist, estimates that only 15% of its BrightStor backup software customers use encryption.
Application-aware encryption. A few encryption products offer some level of integration with the application. These products such as CoreGuard from Vormetric Inc. allow administrators to create policies to encrypt specific files--or even data--associated with specific types of transactions. Downsides include potential degraded server performance. Also, many of these products are available for only certain servers or operating systems.
Inline encryption appliances. These products from vendors such as NeoScale Systems and Decru Inc. offload encryption chores from the application server, moving them to a dedicated hardware appliance that sits in the storage fabric. This approach usually avoids the performance problems associated with software-enabled encryption. The downsides: not all of these devices support all types of storage--network-attached storage, a storage area network and tape--and all are highly proprietary.

Encryption's downside
Before deciding to encrypt, storage managers will have to decide whether degraded performance and interoperability snags are a price worth paying for increased peace of mind. Storage encryption products--mostly from a group of relatively young companies--work in a variety of different ways, and some impact SAN throughput more than others.

And while most storage encryption products make some use of cryptography standards, in most other respects they are highly proprietary and don't interoperate. That means once you select a storage encryption product, it's going to be difficult to switch.

Some storage managers think shoring up SAN security through encryption is worth the trade-offs. United Airlines' Loyalty Services Group in Shaumberg, IL, which runs the company's Web-based booking system, recently decided to deploy an encryption appliance from NeoScale Systems Inc. as part of a project to replace the DAS used to store customer credit card information.

The CryptoStor FC appliance sits directly on the Fibre Channel (FC) wire between the switch and storage devices and encrypts all data as it moves onto disk. The appliance offloads all encryption processing from the application server, and like other storage encryption appliances, it authenticates users attempting to access protected storage and allows administrators to create rules governing which data blocks are encrypted and which ones are not.

United opted for encryption, says Gary Pilafas, senior storage and systems architect, in large part because of expectations that regulators will require the company to prove it's done everything possible to keep customer information private.

"When they come to us and ask what we've put in place to protect customers, we can show them," he says.

So far, Pilafas says the CryptoStor appliance hasn't reduced the performance of his SAN. Because the appliance is transparent to other devices in the SAN fabric and it implements encryption algorithms in hardware, NeoScale claims it's able to perform at nearly 2Gb/s line speeds.

Some storage encryption tools, however, have a larger impact on SAN performance. While appliances such as those from NeoScale and Decru Inc. handle encryption in the hardware and claim nearline-speed performance, others such as the Assurancy SecureData from Kasten Chase and the CoreGuard from Vormetric Inc. require hardware or software agents running on servers in addition to the hardware appliance. This approach generally involves a performance hit. Kasten Chase estimates a 10% impact on SAN Fibre performance. But there's an upside to this approach: It can be more easily scalable.

Performance concerns have kept some organizations away from storage encryption. At Deloitte Consulting, IT managers have considered encrypting storage. With its many clients throughout privacy-conscious Europe, Deloitte could use encryption to reassure regulators, says CTO Eric Eriksen.

"But each time we've looked at it, we've become concerned with the performance issue. The only way to resolve that would be to test some appliances, which we haven't done yet, he says."

In the meantime, Deloitte has used encryption features built into applications such as e-mail to protect some data while in transit.

Application-centric tools
Whether to take a storage-centric approach to encryption or an application-centric approach is another decision security-conscious IT managers will have to make. While some appliances sit directly on the FC and encrypt data on a storage block-by-block basis, other encryption products work much more closely with the application.

Ingrian Networks' Network-Attached Encryption product includes an encryption appliance, but unlike the Decru and NeoScale products, it also works with what Ingrian calls a Secure Transaction Platform--software that sits in front of a Web or application server and monitors files and records passing between those servers and the database server. The Secure Transaction Platform allows IT managers to be more selective about what they're encrypting because it deals with data on a more granular level, as files or records rather than blocks.

Another product, Vormetric's CoreGuard, works in a similar way, with a software agent called Policy Enforcement Module plugging into the operating system's file system. CoreGuard also includes a policy engine, giving administrators the ability to grant or restrict end-user access on a file-by-file basis and to track who's accessed which files and when.

Such application-level encryption and authorization has its advantages. Even competitors admit that besides offering much more fine-grained encryption and access control, such systems also are able to encrypt and protect data from the moment applications generate it.

"If you're running one key application and that's where the bulk of your mission-critical data is, application-level encryption makes sense," says Scott Gordon, NeoScale's VP of marketing.

That's exactly the situation that last year convinced Van Nguyen, director of global IT security at an integrated circuit software design company, to deploy Vormetric's CoreGuard product to encrypt and control access to proprietary source code, the heart of the company's intellectual property. The integrated circuit software company created its own version control software that allows developers at 80 sites in 20 countries to collaborate by sharing files over an IP network. CoreGuard's encryption allows the company to ensure the privacy of the source code. And its access control features allow the company to keep track of who accesses a particular file.

"We looked at some of the storage encryption appliances, but they represented only half of a solution," says Nguyen. "With those, even after you've encrypted the data, there's a lot you can't control."

While application-centric encryption offers more control, there are drawbacks. Because products like Ingrian's rely on software agents, they tend to impact performance more than hardware-only encryption engines. And many application-centric products support only a limited range of environments. Vormetric, for example, only supports applications running on Sun's Solaris operating system. Officials say the company currently is working on a Linux implementation.

Moreover, relying on applications or application-specific tools for encryption can spawn complexity.

Consider a situation where an enterprise had several applications generating critical data that required encryption. The data that had to be integrated came from different applications. If different applications running on different operating systems handled encryption differently, it's likely that data would have to be decrypted before it could be integrated, causing extra overhead and a security risk.

But whether you opt for storage-centric or application-centric approach, you'll have to accept one central fact: All storage encryption products today are highly proprietary. While most use standard encryption algorithms such as the FIPS-approved 256-bit Advanced Encryption Standard as the starting point, they take different approaches to things such as authenticating users and storage devices and clustering. That means storage encryption appliances don't interoperate.

"Encryption appliances right now are point solutions ... once you've selected one, you're pretty much stuck with that approach," says Enterprise Storage Group's Marrone-Hurley. That's because in industries such as healthcare and financial services, organizations are required to retain patient and customer records data for years or even decades. Such organizations must be able to store encryption keys securely for years and find them when they need them. While Neoscale and Decru appliances encrypt tape-bound data, storage managers should think twice before using encryption, particularly for protecting large amounts of data that will be vaulted.

According to W. Curtis Preston, founder of The Storage Group, if encryption appliance vendors were to fail and stop providing support, users with large amounts of archival data on tape could be confronted with the large job of trying to decrypt it. Therefore, Preston says, encryption is a better fit for backup applications involving tape because recovery would be easier.

In either case, says Preston, users considering encryption for tape should ensure the appliance they choose does compression as well as encryption.

"What if [the encryption appliance] were to go away?" says Kevin Granhold, manager of network services at the University of Texas Health Science Center in Houston, which has installed a NeoScale CryptoStorFC to protect patient data stored on a Compaq EMA 12000 SAN.

"Given that the appliance is proprietary and available from only one vendor, we had to make sure that we could make copies of the keys and store them in a secure location," he says.

Adding new features
In response to these concerns, storage encryption vendors have been beefing up their systems' key management capabilities. Last spring, Decru added what it calls "lifetime key management" features to its DataFort appliances. They include clustering and automated key backup, which ensures that keys are always stored in two different appliances. In the event that both appliances are destroyed, Decru also makes a software recovery tool that can be used to decrypt data stored on FC SANs, NAS or tape devices. NeoScale supports similar features.

Such failsafe features have convinced storage managers like United's Pilafas to overlook the proprietary nature of encryption appliances. "I'm not a big fan of proprietary appliances, especially appliances that sit in-band," he says. "They have to make a real good argument. In this case, they did."

Even if a case can be made for storage encryption in your organization, it's important to keep one thing in mind: Encryption should be thought of as just a piece of the storage security puzzle, not as a silver bullet. Besides using encryption to beef up the privacy of data at rest on networked storage devices and in transit, storage managers should also work to develop a coherent set of storage security policies, make sure strong authentication and authorization exists between SAN and NAS fabric elements and create mechanisms for auditing fabric changes.

This was first published in January 2004
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