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Susan Landau published an excellent essay on the current justification for the government breaking end-to-end-encryption: child sexual abuse and exploitation (CSAE). She puts the debate into historical context, discusses the problem of CSAE, and explains why breaking encryption isn’t the solution.
Andy Greenberg wrote a long article—an excerpt from his new book—on how law enforcement de-anonymized bitcoin transactions to take down a global child porn ring.
Within a few years of Bitcoin’s arrival, academic security researchers—and then companies like Chainalysis—began to tear gaping holes in the masks separating Bitcoin users’ addresses and their real-world identities. They could follow bitcoins on the blockchain as they moved from address to address until they reached one that could be tied to a known identity. In some cases, an investigator could learn someone’s Bitcoin addresses by transacting with them, the way an undercover narcotics agent might conduct a buy-and-bust. In other cases, they could trace a target’s coins to an account at a cryptocurrency exchange where financial regulations required users to prove their identity. A quick subpoena to the exchange from one of Chainalysis’ customers in law enforcement was then enough to strip away any illusion of Bitcoin’s anonymity.
Chainalysis had combined these techniques for de-anonymizing Bitcoin users with methods that allowed it to “cluster” addresses, showing that anywhere from dozens to millions of addresses sometimes belonged to a single person or organization. When coins from two or more addresses were spent in a single transaction, for instance, it revealed that whoever created that “multi-input” transaction must have control of both spender addresses, allowing Chainalysis to lump them into a single identity. In other cases, Chainalysis and its users could follow a “peel chain”—a process analogous to tracking a single wad of cash as a user repeatedly pulled it out, peeled off a few bills, and put it back in a different pocket. In those peel chains, bitcoins would be moved out of one address as a fraction was paid to a recipient and then the remainder returned to the spender at a “change” address. Distinguishing those change addresses could allow an investigator to follow a sum of money as it hopped from one address to the next, charting its path through the noise of Bitcoin’s blockchain.
Thanks to tricks like these, Bitcoin had turned out to be practically the opposite of untraceable: a kind of honeypot for crypto criminals that had, for years, dutifully and unerasably recorded evidence of their dirty deals. By 2017, agencies like the FBI, the Drug Enforcement Agency, and the IRS’s Criminal Investigation division (or IRS-CI) had traced Bitcoin transactions to carry out one investigative coup after another, very often with the help of Chainalysis.
Rolling Stone is reporting that the UK government has hired the M&C Saatchi advertising agency to launch an anti-encryption advertising campaign. Presumably they’ll lean heavily on the “think of the children!” rhetoric we’re seeing in this current wave of the crypto wars. The technical eavesdropping mechanisms have shifted to client-side scanning, which won’t actually help—but since that’s not really the point, it’s not argued on its merits.
This is good news:
Whenever you visit a website—even if it’s HTTPS enabled—the DNS query that converts the web address into an IP address that computers can read is usually unencrypted. DNS-over-HTTPS, or DoH, encrypts the request so that it can’t be intercepted or hijacked in order to send a user to a malicious site.
[…]
But the move is not without controversy. Last year, an internet industry group branded Mozilla an “internet villain” for pressing ahead the security feature. The trade group claimed it would make it harder to spot terrorist materials and child abuse imagery. But even some in the security community are split, amid warnings that it could make incident response and malware detection more difficult.
The move to enable DoH by default will no doubt face resistance, but browser makers have argued it’s not a technology that browser makers have shied away from. Firefox became the first browser to implement DoH—with others, like Chrome, Edge, and Opera—quickly following suit.
I think DoH is a great idea, and long overdue.
Slashdot thread. Tech details here. And here’s a good summary of the criticisms.
Back in 1998, Tim May warned us of the “Four Horsemen of the Infocalypse”: “terrorists, pedophiles, drug dealers, and money launderers.” I tended to cast it slightly differently. This is me from 2005:
Beware the Four Horsemen of the Information Apocalypse: terrorists, drug dealers, kidnappers, and child pornographers. Seems like you can scare any public into allowing the government to do anything with those four.
Which particular horseman is in vogue depends on time and circumstance. Since the terrorist attacks of 9/11, the US government has been pushing the terrorist scare story. Recently, it seems to have switched to pedophiles and child exploitation. It began in September, with a long New York Times story on child sex abuse, which included this dig at encryption:
And when tech companies cooperate fully, encryption and anonymization can create digital hiding places for perpetrators. Facebook announced in March plans to encrypt Messenger, which last year was responsible for nearly 12 million of the 18.4 million worldwide reports of child sexual abuse material, according to people familiar with the reports. Reports to the authorities typically contain more than one image, and last year encompassed the record 45 million photos and videos, according to the National Center for Missing and Exploited Children.
(That’s wrong, by the way. Facebook Messenger already has an encrypted option. It’s just not turned on by default, like it is in WhatsApp.)
That was followed up by a conference by the US Department of Justice: “Lawless Spaces: Warrant Proof Encryption and its Impact on Child Exploitation Cases.” US Attorney General William Barr gave a speech on the subject. Then came an open letter to Facebook from Barr and others from the UK and Australia, using “protecting children” as the basis for their demand that the company not implement strong end-to-end encryption. (I signed on to another another open letter in response.) Then, the FBI tried to get Interpol to publish a statement denouncing end-to-end encryption.
This week, the Senate Judiciary Committee held a hearing on backdoors: “Encryption and Lawful Access: Evaluating Benefits and Risks to Public Safety and Privacy.” Video, and written testimonies, are available at the link. Eric Neuenschwander from Apple was there to support strong encryption, but the other witnesses were all against it. New York District Attorney Cyrus Vance was true to form:
In fact, we were never able to view the contents of his phone because of this gift to sex traffickers that came, not from God, but from Apple.
It was a disturbing hearing. The Senators asked technical questions to people who couldn’t answer them. The result was that an adjunct law professor was able to frame the issue of strong encryption as an externality caused by corporate liability dumping, and another example of Silicon Valley’s anti-regulation stance.
Let me be clear. None of us who favor strong encryption is saying that child exploitation isn’t a serious crime, or a worldwide problem. We’re not saying that about kidnapping, international drug cartels, money laundering, or terrorism. We are saying three things. One, that strong encryption is necessary for personal and national security. Two, that weakening encryption does more harm than good. And three, law enforcement has other avenues for criminal investigation than eavesdropping on communications and stored devices. This is one example, where people unraveled a dark-web website and arrested hundreds by analyzing Bitcoin transactions. This is another, where policy arrested members of a WhatsApp group.
So let’s have reasoned policy debates about encryption—debates that are informed by technology. And let’s stop it with the scare stories.
EDITED TO ADD (12/13): The DoD just said that strong encryption is essential for national security.
All DoD issued unclassified mobile devices are required to be password protected using strong passwords. The Department also requires that data-in-transit, on DoD issued mobile devices, be encrypted (e.g. VPN) to protect DoD information and resources. The importance of strong encryption and VPNs for our mobile workforce is imperative. Last October, the Department outlined its layered cybersecurity approach to protect DoD information and resources, including service men and women, when using mobile communications capabilities.
[…]
As the use of mobile devices continues to expand, it is imperative that innovative security techniques, such as advanced encryption algorithms, are constantly maintained and improved to protect DoD information and resources. The Department believes maintaining a domestic climate for state of the art security and encryption is critical to the protection of our national security.
The US Department of Justice unraveled a dark web child-porn website, leading to the arrest of 337 people in at least 18 countries. This was all accomplished not through any backdoors in communications systems, but by analyzing the bitcoin transactions and following the money:
Welcome to Video made money by charging fees in bitcoin, and gave each user a unique bitcoin wallet address when they created an account. Son operated the site as a Tor hidden service, a dark web site with a special address that helps mask the identity of the site’s host and its location. But Son and others made mistakes that allowed law enforcement to track them. For example, according to the indictment, very basic assessments of the Welcome to Video website revealed two unconcealed IP addresses managed by a South Korean internet service provider and assigned to an account that provided service to Son’s home address. When agents searched Son’s residence, they found the server running Welcome to Video.
To “follow the money,” as officials put it in Wednesday’s press conference, law enforcement agents sent fairly small amounts of bitcoin—roughly equivalent at the time to $125 to $290—to the bitcoin wallets Welcome to Video listed for payments. Since the bitcoin blockchain leaves all transactions visible and verifiable, they could observe the currency in these wallets being transferred to another wallet. Law enforcement learned from a bitcoin exchange that the second wallet was registered to Son with his personal phone number and one of his personal email addresses.
Remember this the next time some law enforcement official tells us that they’re powerless to investigate crime without breaking cryptography for everyone.
More news articles. The indictment is here. Some of it is pretty horrifying to read.
News from Australia:
Under the law, internet companies would have the same obligations telephone companies do to help law enforcement agencies, Prime Minister Malcolm Turnbull said. Law enforcement agencies would need warrants to access the communications.
“We’ve got a real problem in that the law enforcement agencies are increasingly unable to find out what terrorists and drug traffickers and pedophile rings are up to because of the very high levels of encryption,” Turnbull told reporters.
“Where we can compel it, we will, but we will need the cooperation from the tech companies,” he added.
Never mind that the law 1) would not achieve the desired results because all the smart “terrorists and drug traffickers and pedophile rings” will simply use a third-party encryption app, and 2) would make everyone else in Australia less secure. But that’s all ground I’ve covered before.
I found this bit amusing:
Asked whether the laws of mathematics behind encryption would trump any new legislation, Mr Turnbull said: “The laws of Australia prevail in Australia, I can assure you of that.
“The laws of mathematics are very commendable but the only law that applies in Australia is the law of Australia.”
Next Turnbull is going to try to legislate that pi = 3.2.
Another article. BoingBoing post.
EDITED TO ADD: More commentary.
The Department of Justice is dropping all charges in a child-porn case rather than release the details of a hack against Tor.
As part of a child pornography investigation, the FBI hacked into over 1,300 computers.
But after Playpen was seized, it wasn’t immediately closed down, unlike previous dark web sites that have been shuttered” by law enforcement. Instead, the FBI ran Playpen from its own servers in Newington, Virginia, from February 20 to March 4, reads a complaint filed against a defendant in Utah. During this time, the FBI deployed what is known as a network investigative technique (NIT), the agency’s term for a hacking tool.
While Playpen was being run out of a server in Virginia, and the hacking tool was infecting targets, “approximately 1300 true internet protocol (IP) addresses were identified during this time,” according to the same complaint.
The FBI seems to have obtained a single warrant, but it’s hard to believe that a legal warrant could allow the police to hack 1,300 different computers. We do know that the FBI is very vague about the extent of its operations in warrant applications. And surely we need actual public debate about this sort of technique.
Also, “Playpen” is a super-creepy name for a child porn site. I feel icky just typing it.
There’s speculation that the FBI is responsible for an exploit that compromised the Tor anonymity service. Note that Tor nodes Browser Bundles installed or updated after June 26 are secure.
Sidebar photo of Bruce Schneier by Joe MacInnis.