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Page 8 of 9

Homomorphic Encryption Breakthrough

Last month, IBM made some pretty brash claims about homomorphic encryption and the future of security. I hate to be the one to throw cold water on the whole thing—as cool as the new discovery is—but it’s important to separate the theoretical from the practical.

Homomorphic cryptosystems are ones where mathematical operations on the ciphertext have regular effects on the plaintext. A normal symmetric cipher—DES, AES, or whatever—is not homomorphic. Assume you have a plaintext P, and you encrypt it with AES to get a corresponding ciphertext C. If you multiply that ciphertext by 2, and then decrypt 2C, you get random gibberish instead of P. If you got something else, like 2P, that would imply some pretty strong nonrandomness properties of AES and no one would trust its security.

The RSA algorithm is different. Encrypt P to get C, multiply C by 2, and then decrypt 2C—and you get 2P. That’s a homomorphism: perform some mathematical operation to the ciphertext, and that operation is reflected in the plaintext. The RSA algorithm is homomorphic with respect to multiplication, something that has to be taken into account when evaluating the security of a security system that uses RSA.

This isn’t anything new. RSA’s homomorphism was known in the 1970s, and other algorithms that are homomorphic with respect to addition have been known since the 1980s. But what has eluded cryptographers is a fully homomorphic cryptosystem: one that is homomorphic under both addition and multiplication and yet still secure. And that’s what IBM researcher Craig Gentry has discovered.

This is a bigger deal than might appear at first glance. Any computation can be expressed as a Boolean circuit: a series of additions and multiplications. Your computer consists of a zillion Boolean circuits, and you can run programs to do anything on your computer. This algorithm means you can perform arbitrary computations on homomorphically encrypted data. More concretely: if you encrypt data in a fully homomorphic cryptosystem, you can ship that encrypted data to an untrusted person and that person can perform arbitrary computations on that data without being able to decrypt the data itself. Imagine what that would mean for cloud computing, or any outsourcing infrastructure: you no longer have to trust the outsourcer with the data.

Unfortunately—you knew that was coming, right?—Gentry’s scheme is completely impractical. It uses something called an ideal lattice as the basis for the encryption scheme, and both the size of the ciphertext and the complexity of the encryption and decryption operations grow enormously with the number of operations you need to perform on the ciphertext—and that number needs to be fixed in advance. And converting a computer program, even a simple one, into a Boolean circuit requires an enormous number of operations. These aren’t impracticalities that can be solved with some clever optimization techniques and a few turns of Moore’s Law; this is an inherent limitation in the algorithm. In one article, Gentry estimates that performing a Google search with encrypted keywords—a perfectly reasonable simple application of this algorithm—would increase the amount of computing time by about a trillion. Moore’s law calculates that it would be 40 years before that homomorphic search would be as efficient as a search today, and I think he’s being optimistic with even this most simple of examples.

Despite this, IBM’s PR machine has been in overdrive about the discovery. Its press release makes it sound like this new homomorphic scheme is going to rewrite the business of computing: not just cloud computing, but “enabling filters to identify spam, even in encrypted email, or protection information contained in electronic medical records.” Maybe someday, but not in my lifetime.

This is not to take anything away anything from Gentry or his discovery. Visions of a fully homomorphic cryptosystem have been dancing in cryptographers’ heads for thirty years. I never expected to see one. It will be years before a sufficient number of cryptographers examine the algorithm that we can have any confidence that the scheme is secure, but—practicality be damned—this is an amazing piece of work.

Posted on July 9, 2009 at 6:36 AM • View Comments

Terrorist Risk of Cloud Computing

I don’t even know where to begin on this one:

As we have seen in the past with other technologies, while cloud resources will likely start out decentralized, as time goes by and economies of scale take hold, they will start to collect into mega-technology hubs. These hubs could, as the end of this cycle, number in the low single digits and carry most of the commerce and data for a nation like ours. Elsewhere, particularly in Europe, those hubs could handle several nations’ public and private data.

And therein lays the risk.

The Twin Towers, which were destroyed in the 9/11 attack, took down a major portion of the U.S. infrastructure at the same time. The capability and coverage of cloud-based mega-hubs would easily dwarf hundreds of Twin Tower-like operations. Although some redundancy would likely exist—hopefully located in places safe from disasters—should a hub be destroyed, it could likely take down a significant portion of the country it supported at the same time.

[…]

Each hub may represent a target more attractive to terrorists than today’s favored nuclear power plants.

It’s only been eight years, and this author thinks that the 9/11 attacks “took down a major portion of the U.S. infrastructure.” That’s just plain ridiculous. I was there (in the U.S, not in New York). The government, the banks, the power system, commerce everywhere except lower Manhattan, the Internet, the water supply, the food supply, and every other part of the U.S. infrastructure I can think of worked just fine during and after the attacks. The New York Stock Exchange was up and running in a few days. Even the piece of our infrastructure that was the most disrupted—the airplane network—was up and running in a week. I think the author of that piece needs to travel to somewhere on the planet where major portions of the infrastructure actually get disrupted, so he can see what it’s like.

No less ridiculous is the main point of the article, which seems to imply that terrorists will someday decide that disrupting people’s Lands’ End purchases will be more attractive than killing them. Okay, that was a caricature of the article, but not by much. Terrorism is an attack against our minds, using random death and destruction as a tactic to cause terror in everyone. To even suggest that data disruption would cause more terror than nuclear fallout completely misunderstands terrorism and terrorists.

And anyway, any e-commerce, banking, etc. site worth anything is backed up and dual-homed. There are lots of risks to our data networks, but physically blowing up a data center isn’t high on the list.

Posted on July 6, 2009 at 6:12 AM • View Comments

Cloud Computing

This year’s overhyped IT concept is cloud computing. Also called software as a service (Saas), cloud computing is when you run software over the internet and access it via a browser. The Salesforce.com customer management software is an example of this. So is Google Docs. If you believe the hype, cloud computing is the future.

But, hype aside, cloud computing is nothing new . It’s the modern version of the timesharing model from the 1960s, which was eventually killed by the rise of the personal computer. It’s what Hotmail and Gmail have been doing all these years, and it’s social networking sites, remote backup companies, and remote email filtering companies such as MessageLabs. Any IT outsourcing—network infrastructure, security monitoring, remote hosting—is a form of cloud computing.

The old timesharing model arose because computers were expensive and hard to maintain. Modern computers and networks are drastically cheaper, but they’re still hard to maintain. As networks have become faster, it is again easier to have someone else do the hard work. Computing has become more of a utility; users are more concerned with results than technical details, so the tech fades into the background.

But what about security? Isn’t it more dangerous to have your email on Hotmail’s servers, your spreadsheets on Google’s, your personal conversations on Facebook’s, and your company’s sales prospects on salesforce.com’s? Well, yes and no.

IT security is about trust. You have to trust your CPU manufacturer, your hardware, operating system and software vendors—and your ISP. Any one of these can undermine your security: crash your systems, corrupt data, allow an attacker to get access to systems. We’ve spent decades dealing with worms and rootkits that target software vulnerabilities. We’ve worried about infected chips. But in the end, we have no choice but to blindly trust the security of the IT providers we use.

Saas moves the trust boundary out one step further—you now have to also trust your software service vendors—but it doesn’t fundamentally change anything. It’s just another vendor we need to trust.

There is one critical difference. When a computer is within your network, you can protect it with other security systems such as firewalls and IDSs. You can build a resilient system that works even if those vendors you have to trust may not be as trustworthy as you like. With any outsourcing model, whether it be cloud computing or something else, you can’t. You have to trust your outsourcer completely. You not only have to trust the outsourcer’s security, but its reliability, its availability, and its business continuity.

You don’t want your critical data to be on some cloud computer that abruptly disappears because its owner goes bankrupt . You don’t want the company you’re using to be sold to your direct competitor. You don’t want the company to cut corners, without warning, because times are tight. Or raise its prices and then refuse to let you have your data back. These things can happen with software vendors, but the results aren’t as drastic.

There are two different types of cloud computing customers. The first only pays a nominal fee for these services—and uses them for free in exchange for ads: e.g., Gmail and Facebook. These customers have no leverage with their outsourcers. You can lose everything. Companies like Google and Amazon won’t spend a lot of time caring. The second type of customer pays considerably for these services: to Salesforce.com, MessageLabs, managed network companies, and so on. These customers have more leverage, providing they write their service contracts correctly. Still, nothing is guaranteed.

Trust is a concept as old as humanity, and the solutions are the same as they have always been. Be careful who you trust, be careful what you trust them with, and be careful how much you trust them. Outsourcing is the future of computing. Eventually we’ll get this right, but you don’t want to be a casualty along the way.

This essay originally appeared in The Guardian.

EDITED TO ADD (6/4): Another opinion.

EDITED TO ADD (6/5): A rebuttal. And an apology for the tone of the rebuttal. The reason I am talking so much about cloud computing is that reporters and inverviewers keep asking me about it. I feel kind of dragged into this whole thing.

EDITED TO ADD (6/6): At the Computers, Freedom, and Privacy conference last week, Bob Gellman said (this, by him, is worth reading) that the nine most important words in cloud computing are: “terms of service,” “location, location, location,” and “provider, provider, provider”—basically making the same point I did. You need to make sure the terms of service you sign up to are ones you can live with. You need to make sure the location of the provider doesn’t subject you to any laws that you can’t live with. And you need to make sure your provider is someone you’re willing to work with. Basically, if you’re going to give someone else your data, you need to trust them.

Posted on June 4, 2009 at 6:14 AM •

An Expectation of Online Privacy

If your data is online, it is not private. Oh, maybe it seems private. Certainly, only you have access to your e-mail. Well, you and your ISP. And the sender’s ISP. And any backbone provider who happens to route that mail from the sender to you. And, if you read your personal mail from work, your company. And, if they have taps at the correct points, the NSA and any other sufficiently well-funded government intelligence organization—domestic and international.

You could encrypt your mail, of course, but few of us do that. Most of us now use webmail. The general problem is that, for the most part, your online data is not under your control. Cloud computing and software as a service exacerbate this problem even more.

Your webmail is less under your control than it would be if you downloaded your mail to your computer. If you use Salesforce.com, you’re relying on that company to keep your data private. If you use Google Docs, you’re relying on Google. This is why the Electronic Privacy Information Center recently filed a complaint with the Federal Trade Commission: many of us are relying on Google’s security, but we don’t know what it is.

This is new. Twenty years ago, if someone wanted to look through your correspondence, he had to break into your house. Now, he can just break into your ISP. Ten years ago, your voicemail was on an answering machine in your office; now it’s on a computer owned by a telephone company. Your financial accounts are on remote websites protected only by passwords; your credit history is collected, stored, and sold by companies you don’t even know exist.

And more data is being generated. Lists of books you buy, as well as the books you look at, are stored in the computers of online booksellers. Your affinity card tells your supermarket what foods you like. What were cash transactions are now credit card transactions. What used to be an anonymous coin tossed into a toll booth is now an EZ Pass record of which highway you were on, and when. What used to be a face-to-face chat is now an e-mail, IM, or SMS conversation—or maybe a conversation inside Facebook.

Remember when Facebook recently changed its terms of service to take further control over your data? They can do that whenever they want, you know.

We have no choice but to trust these companies with our security and privacy, even though they have little incentive to protect them. Neither ChoicePoint, Lexis Nexis, Bank of America, nor T-Mobile bears the costs of privacy violations or any resultant identity theft.

This loss of control over our data has other effects, too. Our protections against police abuse have been severely watered down. The courts have ruled that the police can search your data without a warrant, as long as others hold that data. If the police want to read the e-mail on your computer, they need a warrant; but they don’t need one to read it from the backup tapes at your ISP.

This isn’t a technological problem; it’s a legal problem. The courts need to recognize that in the information age, virtual privacy and physical privacy don’t have the same boundaries. We should be able to control our own data, regardless of where it is stored. We should be able to make decisions about the security and privacy of that data, and have legal recourse should companies fail to honor those decisions. And just as the Supreme Court eventually ruled that tapping a telephone was a Fourth Amendment search, requiring a warrant—even though it occurred at the phone company switching office and not in the target’s home or office—the Supreme Court must recognize that reading personal e-mail at an ISP is no different.

This essay was originally published on the SearchSecurity.com website, as the second half of a point/counterpoint with Marcus Ranum.

Posted on May 5, 2009 at 6:06 AM • View Comments

Unfair and Deceptive Data Trade Practices

Do you know what your data did last night? Almost none of the more than 27 million people who took the RealAge quiz realized that their personal health data was being used by drug companies to develop targeted e-mail marketing campaigns.

There’s a basic consumer protection principle at work here, and it’s the concept of “unfair and deceptive” trade practices. Basically, a company shouldn’t be able to say one thing and do another: sell used goods as new, lie on ingredients lists, advertise prices that aren’t generally available, claim features that don’t exist, and so on.

Buried in RealAge’s 2,400-word privacy policy is this disclosure: “If you elect to say yes to becoming a free RealAge Member, we will periodically send you free newsletters and e-mails that directly promote the use of our site(s) or the purchase of our products or services and may contain, in whole or in part, advertisements for third parties which relate to marketed products of selected RealAge partners.”

They maintain that when you join the website, you consent to receiving pharmaceutical company spam. But since that isn’t spelled out, it’s not really informed consent. That’s deceptive.

Cloud computing is another technology where users entrust their data to service providers. Salesforce.com, Gmail, and Google Docs are examples; your data isn’t on your computer—it’s out in the “cloud” somewhere—and you access it from your web browser. Cloud computing has significant benefits for customers and huge profit potential for providers. It’s one of the fastest growing IT market segments—69% of Americans now use some sort of cloud computing services—but the business is rife with shady, if not outright deceptive, advertising.

Take Google, for example. Last month, the Electronic Privacy Information Center (I’m on its board of directors) filed a complaint with the Federal Trade Commission concerning Google’s cloud computing services. On its website, Google repeatedly assures customers that their data is secure and private, while published vulnerabilities demonstrate that it is not. Google’s not foolish, though; its Terms of Service explicitly disavow any warranty or any liability for harm that might result from Google’s negligence, recklessness, malevolent intent, or even purposeful disregard of existing legal obligations to protect the privacy and security of user data. EPIC claims that’s deceptive.

Facebook isn’t much better. Its plainly written (and not legally binding) Statement of Principles contains an admirable set of goals, but its denser and more legalistic Statement of Rights and Responsibilities undermines a lot of it. One research group who studies these documents called it “democracy theater“: Facebook wants the appearance of involving users in governance, without the messiness of actually having to do so. Deceptive.

These issues are not identical. RealAge is hiding what it does with your data. Google is trying to both assure you that your data is safe and duck any responsibility when it’s not. Facebook wants to market a democracy but run a dictatorship. But they all involve trying to deceive the customer.

Cloud computing services like Google Docs, and social networking sites like RealAge and Facebook, bring with them significant privacy and security risks over and above traditional computing models. Unlike data on my own computer, which I can protect to whatever level I believe prudent, I have no control over any of these sites, nor any real knowledge of how these companies protect my privacy and security. I have to trust them.

This may be fine—the advantages might very well outweigh the risks—but users often can’t weigh the trade-offs because these companies are going out of their way to hide the risks.

Of course, companies don’t want people to make informed decisions about where to leave their personal data. RealAge wouldn’t get 27 million members if its webpage clearly stated “you are signing up to receive e-mails containing advertising from pharmaceutical companies,” and Google Docs wouldn’t get five million users if its webpage said “We’ll take some steps to protect your privacy, but you can’t blame us if something goes wrong.”

And of course, trust isn’t black and white. If, for example, Amazon tried to use customer credit card info to buy itself office supplies, we’d all agree that that was wrong. If it used customer names to solicit new business from their friends, most of us would consider this wrong. When it uses buying history to try to sell customers new books, many of us appreciate the targeted marketing. Similarly, no one expects Google’s security to be perfect. But if it didn’t fix known vulnerabilities, most of us would consider that a problem.

This is why understanding is so important. For markets to work, consumers need to be able to make informed buying decisions. They need to understand both the costs and benefits of the products and services they buy. Allowing sellers to manipulate the market by outright lying, or even by hiding vital information, about their products breaks capitalism—and that’s why the government has to step in to ensure markets work smoothly.

Last month, Mary K. Engle, Acting Deputy Director of the FTC’s Bureau of Consumer Protection said: “a company’s marketing materials must be consistent with the nature of the product being offered. It’s not enough to disclose the information only in a fine print of a lengthy online user agreement.” She was speaking about Digital Rights Management and, specifically, an incident where Sony used a music copy protection scheme without disclosing that it secretly installed software on customers’ computers. DRM is different from cloud computing or even online surveys and quizzes, but the principle is the same.

Engle again: “if your advertising giveth and your EULA [license agreement] taketh away don’t be surprised if the FTC comes calling.” That’s the right response from government.

A version of this article originally appeared on The Wall Street Journal.

EDITED TO ADD (2/29): Two rebuttals.

Posted on April 27, 2009 at 6:16 AM • View Comments

Third Parties Controlling Information

Wine Therapy is a web bulletin board for serious wine geeks. It’s been active since 2000, and its database of back posts and comments is a wealth of information: tasting notes, restaurant recommendations, stories and so on. Late last year someone hacked the board software, got administrative privileges and deleted the database. There was no backup.

Of course the board’s owner should have been making backups all along, but he has been very sick for the past year and wasn’t able to. And the Internet Archive has been only somewhat helpful.

More and more, information we rely on—either created by us or by others—is out of our control. It’s out there on the internet, on someone else’s website and being cared for by someone else. We use those websites, sometimes daily, and don’t even think about their reliability.

Bits and pieces of the web disappear all the time. It’s called “link rot,” and we’re all used to it. A friend saved 65 links in 1999 when he planned a trip to Tuscany; only half of them still work today. In my own blog, essays and news articles and websites that I link to regularly disappear—sometimes within a few days of my linking to them.

It may be because of a site’s policies—some newspapers only have a couple of weeks on their website—or it may be more random: Position papers disappear off a politician’s website after he changes his mind on an issue, corporate literature disappears from the company’s website after an embarrassment, etc. The ultimate link rot is “site death,” where entire websites disappear: Olympic and World Cup events after the games are over, political candidates’ websites after the elections are over, corporate websites after the funding runs out and so on.

Mostly, we ignore the issue. Sometimes I save a copy of a good recipe I find, or an article relevant to my research, but mostly I trust that whatever I want will be there next time. Were I planning a trip to Tuscany, I would rather search for relevant articles today than rely on a nine-year-old list anyway. Most of the time, link rot and site death aren’t really a problem.

This is changing in a Web 2.0 world, with websites that are less about information and more about community. We help build these sites, with our posts or our comments. We visit them regularly and get to know others who also visit regularly. They become part of our socialization on the internet and the loss of them affects us differently, as Greatest Journal users discovered in January when their site died.

Few, if any, of the people who made Wine Therapy their home kept backup copies of their own posts and comments. I’m sure they didn’t even think of it. I don’t think of it, when I post to the various boards and blogs and forums I frequent. Of course I know better, but I think of these forums as extensions of my own computer—until they disappear.

As we rely on others to maintain our writings and our relationships, we lose control over their availability. Of course, we also lose control over their security, as MySpace users learned last month when a 17-GB file of half a million supposedly private photos was uploaded to a BitTorrent site.

In the early days of the web, I remember feeling giddy over the wealth of information out there and how easy it was to get to. “The internet is my hard drive,” I told newbies. It’s even more true today; I don’t think I could write without so much information so easily accessible. But it’s a pretty damned unreliable hard drive.

The internet is my hard drive, but only if my needs are immediate and my requirements can be satisfied inexactly. It was easy for me to search for information about the MySpace photo hack. And it will be easy to look up, and respond to, comments to this essay, both on Wired.com and on my own blog. Wired.com is a commercial venture, so there is advertising value in keeping everything accessible. My site is not at all commercial, but there is personal value in keeping everything accessible. By that analysis, all sites should be up on the internet forever, although that’s certainly not true. What is true is that there’s no way to predict what will disappear when.

Unfortunately, there’s not much we can do about it. The security measures largely aren’t in our hands. We can save copies of important web pages locally, and copies of anything important we post. The Internet Archive is remarkably valuable in saving bits and pieces of the internet. And recently, we’ve started seeing tools for archiving information and pages from social networking sites. But what’s really important is the whole community, and we don’t know which bits we want until they’re no longer there.

And about Wine Therapy, I think it started in 2000. It might have been 2001. I can’t check, because someone erased the archives.

This essay originally appeared on Wired.com.

Posted on February 27, 2008 at 5:46 AM • View Comments

Freakonomics Q&A

I just did a Q&A on the Freakonomics blog. Nothing regular readers of this blog haven’t heard before, but it was fun all the same. There’s also a Slashdot thread on the Q&A.

Posted on December 5, 2007 at 9:10 AM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.