Entries Tagged "censorship"
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Security researchers have recently discovered a botnet with a novel defense against takedowns. Normally, authorities can disable a botnet by taking over its command-and-control server. With nowhere to go for instructions, the botnet is rendered useless. But over the years, botnet designers have come up with ways to make this counterattack harder. Now the content-delivery network Akamai has reported on a new method: a botnet that uses the Bitcoin blockchain ledger. Since the blockchain is globally accessible and hard to take down, the botnet’s operators appear to be safe.
It’s best to avoid explaining the mathematics of Bitcoin’s blockchain, but to understand the colossal implications here, you need to understand one concept. Blockchains are a type of “distributed ledger”: a record of all transactions since the beginning, and everyone using the blockchain needs to have access to — and reference — a copy of it. What if someone puts illegal material in the blockchain? Either everyone has a copy of it, or the blockchain’s security fails.
To be fair, not absolutely everyone who uses a blockchain holds a copy of the entire ledger. Many who buy cryptocurrencies like Bitcoin and Ethereum don’t bother using the ledger to verify their purchase. Many don’t actually hold the currency outright, and instead trust an exchange to do the transactions and hold the coins. But people need to continually verify the blockchain’s history on the ledger for the system to be secure. If they stopped, then it would be trivial to forge coins. That’s how the system works.
Some years ago, people started noticing all sorts of things embedded in the Bitcoin blockchain. There are digital images, including one of Nelson Mandela. There’s the Bitcoin logo, and the original paper describing Bitcoin by its alleged founder, the pseudonymous Satoshi Nakamoto. There are advertisements, and several prayers. There’s even illegal pornography and leaked classified documents. All of these were put in by anonymous Bitcoin users. But none of this, so far, appears to seriously threaten those in power in governments and corporations. Once someone adds something to the Bitcoin ledger, it becomes sacrosanct. Removing something requires a fork of the blockchain, in which Bitcoin fragments into multiple parallel cryptocurrencies (and associated blockchains). Forks happen, rarely, but never yet because of legal coercion. And repeated forking would destroy Bitcoin’s stature as a stable(ish) currency.
The botnet’s designers are using this idea to create an unblockable means of coordination, but the implications are much greater. Imagine someone using this idea to evade government censorship. Most Bitcoin mining happens in China. What if someone added a bunch of Chinese-censored Falun Gong texts to the blockchain?<
What if someone added a type of political speech that Singapore routinely censors? Or cartoons that Disney holds the copyright to?
In Bitcoin’s and most other public blockchains there are no central, trusted authorities. Anyone in the world can perform transactions or become a miner. Everyone is equal to the extent that they have the hardware and electricity to perform cryptographic computations.
This openness is also a vulnerability, one that opens the door to asymmetric threats and small-time malicious actors. Anyone can put information in the one and only Bitcoin blockchain. Again, that’s how the system works.
Over the last three decades, the world has witnessed the power of open networks: blockchains, social media, the very web itself. What makes them so powerful is that their value is related not just to the number of users, but the number of potential links between users. This is Metcalfe’s law — value in a network is quadratic, not linear, in the number of users — and every open network since has followed its prophecy.
As Bitcoin has grown, its monetary value has skyrocketed, even if its uses remain unclear. With no barrier to entry, the blockchain space has been a Wild West of innovation and lawlessness. But today, many prominent advocates suggest Bitcoin should become a global, universal currency. In this context, asymmetric threats like embedded illegal data become a major challenge.
The philosophy behind Bitcoin traces to the earliest days of the open internet. Articulated in John Perry Barlow’s 1996 Declaration of the Independence of Cyberspace, it was and is the ethos of tech startups: Code is more trustworthy than institutions. Information is meant to be free, and nobody has the right — and should not have the ability — to control it.
But information must reside somewhere. Code is written by and for people, stored on computers located within countries, and embedded within the institutions and societies we have created. To trust information is to trust its chain of custody and the social context it comes from. Neither code nor information is value-neutral, nor ever free of human context.
Today, Barlow’s vision is a mere shadow; every society controls the information its people can access. Some of this control is through overt censorship, as China controls information about Taiwan, Tiananmen Square, and the Uyghurs. Some of this is through civil laws designed by the powerful for their benefit, as with Disney and US copyright law, or UK libel law.
Bitcoin and blockchains like it are on a collision course with these laws. What happens when the interests of the powerful, with the law on their side, are pitted against an open blockchain? Let’s imagine how our various scenarios might play out.
China first: In response to Falun Gong texts in the blockchain, the People’s Republic decrees that any miners processing blocks with banned content will be taken offline — their IPs will be blacklisted. This causes a hard fork of the blockchain at the point just before the banned content. China might do this under the guise of a “patriotic” messaging campaign, publicly stating that it’s merely maintaining financial sovereignty from Western banks. Then it uses paid influencers and moderators on social media to pump the China Bitcoin fork, through both partisan comments and transactions. Two distinct forks would soon emerge, one behind China’s Great Firewall and one outside. Other countries with similar governmental and media ecosystems — Russia, Singapore, Myanmar — might consider following suit, creating multiple national Bitcoin forks. These would operate independently, under mandates to censor unacceptable transactions from then on.
Disney’s approach would play out differently. Imagine the company announces it will sue any ISP that hosts copyrighted content, starting with networks hosting the biggest miners. (Disney has sued to enforce its intellectual property rights in China before.) After some legal pressure, the networks cut the miners off. The miners reestablish themselves on another network, but Disney keeps the pressure on. Eventually miners get pushed further and further off of mainstream network providers, and resort to tunneling their traffic through an anonymity service like Tor. That causes a major slowdown in the already slow (because of the mathematics) Bitcoin network. Disney might issue takedown requests for Tor exit nodes, causing the network to slow to a crawl. It could persist like this for a long time without a fork. Or the slowdown could cause people to jump ship, either by forking Bitcoin or switching to another cryptocurrency without the copyrighted content.
And then there’s illegal pornographic content and leaked classified data. These have been on the Bitcoin blockchain for over five years, and nothing has been done about it. Just like the botnet example, it may be that these do not threaten existing power structures enough to warrant takedowns. This could easily change if Bitcoin becomes a popular way to share child sexual abuse material. Simply having these illegal images on your hard drive is a felony, which could have significant repercussions for anyone involved in Bitcoin.
Whichever scenario plays out, this may be the Achilles heel of Bitcoin as a global currency.
If an open network such as a blockchain were threatened by a powerful organization — China’s censors, Disney’s lawyers, or the FBI trying to take down a more dangerous botnet — it could fragment into multiple networks. That’s not just a nuisance, but an existential risk to Bitcoin.
Suppose Bitcoin were fragmented into 10 smaller blockchains, perhaps by geography: one in China, another in the US, and so on. These fragments might retain their original users, and by ordinary logic, nothing would have changed. But Metcalfe’s law implies that the overall value of these blockchain fragments combined would be a mere tenth of the original. That is because the value of an open network relates to how many others you can communicate with — and, in a blockchain, transact with. Since the security of bitcoin currency is achieved through expensive computations, fragmented blockchains are also easier to attack in a conventional manner — through a 51 percent attack — by an organized attacker. This is especially the case if the smaller blockchains all use the same hash function, as they would here.
Traditional currencies are generally not vulnerable to these sorts of asymmetric threats. There are no viable small-scale attacks against the US dollar, or almost any other fiat currency. The institutions and beliefs that give money its value are deep-seated, despite instances of currency hyperinflation.
The only notable attacks against fiat currencies are in the form of counterfeiting. Even in the past, when counterfeit bills were common, attacks could be thwarted. Counterfeiters require specialized equipment and are vulnerable to law enforcement discovery and arrest. Furthermore, most money today — even if it’s nominally in a fiat currency — doesn’t exist in paper form.
Bitcoin attracted a following for its openness and immunity from government control. Its goal is to create a world that replaces cultural power with cryptographic power: verification in code, not trust in people. But there is no such world. And today, that feature is a vulnerability. We really don’t know what will happen when the human systems of trust come into conflict with the trustless verification that make blockchain currencies unique. Just last week we saw this exact attack on smaller blockchains — not Bitcoin yet. We are watching a public socio-technical experiment in the making, and we will witness its success or failure in the not-too-distant future.
This essay was written with Barath Raghavan, and previously appeared on Wired.com.
EDITED TO ADD (4/14): A research paper on erasing data from Bitcoin blockchain.
There’s a serious debate on reforming Section 230 of the Communications Decency Act. I am in the process of figuring out what I believe, and this is more a place to put resources and listen to people’s comments.
The EFF has written extensively on why it is so important and dismantling it will be catastrophic for the Internet. Danielle Citron disagrees. (There’s also this law journal article by Citron and Ben Wittes.) Sarah Jeong’s op-ed. Another op-ed. Another paper.
Reading all of this, I am reminded of this decade-old quote by Dan Geer. He’s addressing Internet service providers:
Hello, Uncle Sam here.
You can charge whatever you like based on the contents of what you are carrying, but you are responsible for that content if it is illegal; inspecting brings with it a responsibility for what you learn.
You can enjoy common carrier protections at all times, but you can neither inspect nor act on the contents of what you are carrying and can only charge for carriage itself. Bits are bits.
Choose wisely. No refunds or exchanges at this window.
We can revise this choice for the social-media age:
Hi Facebook/Twitter/YouTube/everyone else:
You can build a communications based on inspecting user content and presenting it as you want, but that business model also conveys responsibility for that content.
You can be a communications service and enjoy the protections of CDA 230, in which case you cannot inspect or control the content you deliver.
Facebook would be an example of the former. WhatsApp would be an example of the latter.
I am honestly undecided about all of this. I want CDA230 to protect things like the commenting section of this blog. But I don’t think it should protect dating apps when they are used as a conduit for abuse. And I really don’t want society to pay the cost for all the externalities inherent in Facebook’s business model.
TITLE EDITED TO REDUCE CONFUSION.
My Applied Cryptography is on a list of books banned in Oregon prisons. It’s not me — and it’s not cryptography — it’s that the prisons ban books that teach people to code. The subtitle is “Algorithms, Protocols, and Source Code in C” — and that’s the reason.
My more recent Cryptography Engineering is a much better book for prisoners, anyway.
In my book Data and Goliath, I write about the value of privacy. I talk about how it is essential for political liberty and justice, and for commercial fairness and equality. I talk about how it increases personal freedom and individual autonomy, and how the lack of it makes us all less secure. But this is probably the most important argument as to why society as a whole must protect privacy: it allows society to progress.
We know that surveillance has a chilling effect on freedom. People change their behavior when they live their lives under surveillance. They are less likely to speak freely and act individually. They self-censor. They become conformist. This is obviously true for government surveillance, but is true for corporate surveillance as well. We simply aren’t as willing to be our individual selves when others are watching.
Let’s take an example: hearing that parents and children are being separated as they cross the US border, you want to learn more. You visit the website of an international immigrants’ rights group, a fact that is available to the government through mass Internet surveillance. You sign up for the group’s mailing list, another fact that is potentially available to the government. The group then calls or e-mails to invite you to a local meeting. Same. Your license plates can be collected as you drive to the meeting; your face can be scanned and identified as you walk into and out of the meeting. If, instead of visiting the website, you visit the group’s Facebook page, Facebook knows that you did and that feeds into its profile of you, available to advertisers and political activists alike. Ditto if you like their page, share a link with your friends, or just post about the issue.
Maybe you are an immigrant yourself, documented or not. Or maybe some of your family is. Or maybe you have friends or coworkers who are. How likely are you to get involved if you know that your interest and concern can be gathered and used by government and corporate actors? What if the issue you are interested in is pro- or anti-gun control, anti-police violence or in support of the police? Does that make a difference?
Maybe the issue doesn’t matter, and you would never be afraid to be identified and tracked based on your political or social interests. But even if you are so fearless, you probably know someone who has more to lose, and thus more to fear, from their personal, sexual, or political beliefs being exposed.
This isn’t just hypothetical. In the months and years after the 9/11 terrorist attacks, many of us censored what we spoke about on social media or what we searched on the Internet. We know from a 2013 PEN study that writers in the United States self-censored their browsing habits out of fear the government was watching. And this isn’t exclusively an American event; Internet self-censorship is prevalent across the globe, China being a prime example.
Ultimately, this fear stagnates society in two ways. The first is that the presence of surveillance means society cannot experiment with new things without fear of reprisal, and that means those experiments — if found to be inoffensive or even essential to society — cannot slowly become commonplace, moral, and then legal. If surveillance nips that process in the bud, change never happens. All social progress — from ending slavery to fighting for women’s rights — began as ideas that were, quite literally, dangerous to assert. Yet without the ability to safely develop, discuss, and eventually act on those assertions, our society would not have been able to further its democratic values in the way that it has.
Consider the decades-long fight for gay rights around the world. Within our lifetimes we have made enormous strides to combat homophobia and increase acceptance of queer folks’ right to marry. Queer relationships slowly progressed from being viewed as immoral and illegal, to being viewed as somewhat moral and tolerated, to finally being accepted as moral and legal.
In the end, it was the public nature of those activities that eventually slayed the bigoted beast, but the ability to act in private was essential in the beginning for the early experimentation, community building, and organizing.
Marijuana legalization is going through the same process: it’s currently sitting between somewhat moral, and — depending on the state or country in question — tolerated and legal. But, again, for this to have happened, someone decades ago had to try pot and realize that it wasn’t really harmful, either to themselves or to those around them. Then it had to become a counterculture, and finally a social and political movement. If pervasive surveillance meant that those early pot smokers would have been arrested for doing something illegal, the movement would have been squashed before inception. Of course the story is more complicated than that, but the ability for members of society to privately smoke weed was essential for putting it on the path to legalization.
We don’t yet know which subversive ideas and illegal acts of today will become political causes and positive social change tomorrow, but they’re around. And they require privacy to germinate. Take away that privacy, and we’ll have a much harder time breaking down our inherited moral assumptions.
The second way surveillance hurts our democratic values is that it encourages society to make more things illegal. Consider the things you do — the different things each of us does — that portions of society find immoral. Not just recreational drugs and gay sex, but gambling, dancing, public displays of affection. All of us do things that are deemed immoral by some groups, but are not illegal because they don’t harm anyone. But it’s important that these things can be done out of the disapproving gaze of those who would otherwise rally against such practices.
If there is no privacy, there will be pressure to change. Some people will recognize that their morality isn’t necessarily the morality of everyone — and that that’s okay. But others will start demanding legislative change, or using less legal and more violent means, to force others to match their idea of morality.
It’s easy to imagine the more conservative (in the small-c sense, not in the sense of the named political party) among us getting enough power to make illegal what they would otherwise be forced to witness. In this way, privacy helps protect the rights of the minority from the tyranny of the majority.
This is how we got Prohibition in the 1920s, and if we had had today’s surveillance capabilities in the 1920s, it would have been far more effectively enforced. Recipes for making your own spirits would have been much harder to distribute. Speakeasies would have been impossible to keep secret. The criminal trade in illegal alcohol would also have been more effectively suppressed. There would have been less discussion about the harms of Prohibition, less “what if we didn’t?” thinking. Political organizing might have been difficult. In that world, the law might have stuck to this day.
China serves as a cautionary tale. The country has long been a world leader in the ubiquitous surveillance of its citizens, with the goal not of crime prevention but of social control. They are about to further enhance their system, giving every citizen a “social credit” rating. The details are yet unclear, but the general concept is that people will be rated based on their activities, both online and off. Their political comments, their friends and associates, and everything else will be assessed and scored. Those who are conforming, obedient, and apolitical will be given high scores. People without those scores will be denied privileges like access to certain schools and foreign travel. If the program is half as far-reaching as early reports indicate, the subsequent pressure to conform will be enormous. This social surveillance system is precisely the sort of surveillance designed to maintain the status quo.
For social norms to change, people need to deviate from these inherited norms. People need the space to try alternate ways of living without risking arrest or social ostracization. People need to be able to read critiques of those norms without anyone’s knowledge, discuss them without their opinions being recorded, and write about their experiences without their names attached to their words. People need to be able to do things that others find distasteful, or even immoral. The minority needs protection from the tyranny of the majority.
Privacy makes all of this possible. Privacy encourages social progress by giving the few room to experiment free from the watchful eye of the many. Even if you are not personally chilled by ubiquitous surveillance, the society you live in is, and the personal costs are unequivocal.
The Center for Human Rights in Iran has released a report outlining the effect’s of that country’s ban on Telegram, a secure messaging app used by about half of the country.
The ban will disrupt the most important, uncensored platform for information and communication in Iran, one that is used extensively by activists, independent and citizen journalists, dissidents and international media. It will also impact electoral politics in Iran, as centrist, reformist and other relatively moderate political groups that are allowed to participate in Iran’s elections have been heavily and successfully using Telegram to promote their candidates and electoral lists during elections. State-controlled domestic apps and media will not provide these groups with such a platform, even as they continue to do so for conservative and hardline political forces in the country, significantly aiding the latter.
From a Wired article:
Researchers found that the ban has had broad effects, hindering and chilling individual speech, forcing political campaigns to turn to state-sponsored media tools, limiting journalists and activists, curtailing international interactions, and eroding businesses that grew their infrastructure and reach off of Telegram.
It’s interesting that the analysis doesn’t really center around the security properties of Telegram, but more around its ubiquity as a messaging platform in the country.
Internet censors have a new strategy in their bid to block applications and websites: pressuring the large cloud providers that host them. These providers have concerns that are much broader than the targets of censorship efforts, so they have the choice of either standing up to the censors or capitulating in order to maximize their business. Today’s Internet largely reflects the dominance of a handful of companies behind the cloud services, search engines and mobile platforms that underpin the technology landscape. This new centralization radically tips the balance between those who want to censor parts of the Internet and those trying to evade censorship. When the profitable answer is for a software giant to acquiesce to censors’ demands, how long can Internet freedom last?
The recent battle between the Russian government and the Telegram messaging app illustrates one way this might play out. Russia has been trying to block Telegram since April, when a Moscow court banned it after the company refused to give Russian authorities access to user messages. Telegram, which is widely used in Russia, works on both iPhone and Android, and there are Windows and Mac desktop versions available. The app offers optional end-to-end encryption, meaning that all messages are encrypted on the sender’s phone and decrypted on the receiver’s phone; no part of the network can eavesdrop on the messages.
Since then, Telegram has been playing cat-and-mouse with the Russian telecom regulator Roskomnadzor by varying the IP address the app uses to communicate. Because Telegram isn’t a fixed website, it doesn’t need a fixed IP address. Telegram bought tens of thousands of IP addresses and has been quickly rotating through them, staying a step ahead of censors. Cleverly, this tactic is invisible to users. The app never sees the change, or the entire list of IP addresses, and the censor has no clear way to block them all.
A week after the court ban, Roskomnadzor countered with an unprecedented move of its own: blocking 19 million IP addresses, many on Amazon Web Services and Google Cloud. The collateral damage was widespread: The action inadvertently broke many other web services that use those platforms, and Roskomnadzor scaled back after it became clear that its action had affected services critical for Russian business. Even so, the censor is still blocking millions of IP addresses.
More recently, Russia has been pressuring Apple not to offer the Telegram app in its iPhone App Store. As of this writing, Apple has not complied, and the company has allowed Telegram to download a critical software update to iPhone users (after what the app’s founder called a delay last month). Roskomnadzor could further pressure Apple, though, including by threatening to turn off its entire iPhone app business in Russia.
Telegram might seem a weird app for Russia to focus on. Those of us who work in security don’t recommend the program, primarily because of the nature of its cryptographic protocols. In general, proprietary cryptography has numerous fatal security flaws. We generally recommend Signal for secure SMS messaging, or, if having that program on your computer is somehow incriminating, WhatsApp. (More than 1.5 billion people worldwide use WhatsApp.) What Telegram has going for it is that it works really well on lousy networks. That’s why it is so popular in places like Iran and Afghanistan. (Iran is also trying to ban the app.)
What the Russian government doesn’t like about Telegram is its anonymous broadcast feature — channel capability and chats — which makes it an effective platform for political debate and citizen journalism. The Russians might not like that Telegram is encrypted, but odds are good that they can simply break the encryption. Telegram’s role in facilitating uncontrolled journalism is the real issue.
Iran attempts to block Telegram have been more successful than Russia’s, less because Iran’s censorship technology is more sophisticated but because Telegram is not willing to go as far to defend Iranian users. The reasons are not rooted in business decisions. Simply put, Telegram is a Russian product and the designers are more motivated to poke Russia in the eye. Pavel Durov, Telegram’s founder, has pledged millions of dollars to help fight Russian censorship.
For the moment, Russia has lost. But this battle is far from over. Russia could easily come back with more targeted pressure on Google, Amazon and Apple. A year earlier, Zello used the same trick Telegram is using to evade Russian censors. Then, Roskomnadzor threatened to block all of Amazon Web Services and Google Cloud; and in that instance, both companies forced Zello to stop its IP-hopping censorship-evasion tactic.
Russia could also further develop its censorship infrastructure. If its capabilities were as finely honed as China’s, it would be able to more effectively block Telegram from operating. Right now, Russia can block only specific IP addresses, which is too coarse a tool for this issue. Telegram’s voice capabilities in Russia are significantly degraded, however, probably because high-capacity IP addresses are easier to block.
Whatever its current frustrations, Russia might well win in the long term. By demonstrating its willingness to suffer the temporary collateral damage of blocking major cloud providers, it prompted cloud providers to block another and more effective anti-censorship tactic, or at least accelerated the process. In April, Google and Amazon banned — and technically blocked — the practice of “domain fronting,” a trick anti-censorship tools use to get around Internet censors by pretending to be other kinds of traffic. Developers would use popular websites as a proxy, routing traffic to their own servers through another website — in this case Google.com — to fool censors into believing the traffic was intended for Google.com. The anonymous web-browsing tool Tor has used domain fronting since 2014. Signal, since 2016. Eliminating the capability is a boon to censors worldwide.
Tech giants have gotten embroiled in censorship battles for years. Sometimes they fight and sometimes they fold, but until now there have always been options. What this particular fight highlights is that Internet freedom is increasingly in the hands of the world’s largest Internet companies. And while freedom may have its advocates — the American Civil Liberties Union has tweeted its support for those companies, and some 12,000 people in Moscow protested against the Telegram ban — actions such as disallowing domain fronting illustrate that getting the big tech companies to sacrifice their near-term commercial interests will be an uphill battle. Apple has already removed anti-censorship apps from its Chinese app store.
In 1993, John Gilmore famously said that “The Internet interprets censorship as damage and routes around it.” That was technically true when he said it but only because the routing structure of the Internet was so distributed. As centralization increases, the Internet loses that robustness, and censorship by governments and companies becomes easier.
This essay previously appeared on Lawfare.com.
Interesting research: Sebastian Hellmeier, “The Dictator’s Digital Toolkit: Explaining Variation in Internet Filtering in Authoritarian Regimes,” Politics & Policy, 2016 (full paper is behind a paywall):
Abstract: Following its global diffusion during the last decade, the Internet was expected to become a liberation technology and a threat for autocratic regimes by facilitating collective action. Recently, however, autocratic regimes took control of the Internet and filter online content. Building on the literature concerning the political economy of repression, this article argues that regime characteristics, economic conditions, and conflict in bordering states account for variation in Internet filtering levels among autocratic regimes. Using OLS-regression, the article analyzes the determinants of Internet filtering as measured by the Open Net Initiative in 34 autocratic regimes. The results show that monarchies, regimes with higher levels of social unrest, regime changes in neighboring countries, and less oppositional competition in the political arena are more likely to filter the Internet. The article calls for a systematic data collection to analyze the causal mechanisms and the temporal dynamics of Internet filtering.
Signal, the encrypted messaging app I prefer, is being blocked in both Egypt and the UAE. Recently, the Signal team developed a workaround: domain fronting.
Signal’s new anti-censorship feature uses a trick called “domain fronting,” Marlinspike explains. A country like Egypt, with only a few small internet service providers tightly controlled by the government, can block any direct request to a service on its blacklist. But clever services can circumvent that censorship by hiding their traffic inside of encrypted connections to a major internet service, like the content delivery networks (CDNs) that host content closer to users to speed up their online experience — or in Signal’s case, Google’s App Engine platform, designed to host apps on Google’s servers.
“Now when people in Egypt or the United Arab Emirates send a Signal message, it’ll look identical to something like a Google search,” Marlinspike says. “The idea is that using Signal will look like using Google; if you want to block Signal you’ll have to block Google.”
The trick works because Google’s App Engine allows developers to redirect traffic from Google.com to their own domain. Google’s use of TLS encryption means that contents of the traffic, including that redirect request, are hidden, and the internet service provider can see only that someone has connected to Google.com. That essentially turns Google into a proxy for Signal, bouncing its traffic and fooling the censors.
This isn’t a new trick (Tor uses it too, for example), but it does work.
Sidebar photo of Bruce Schneier by Joe MacInnis.