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More on Kaspersky and the Stolen NSA Attack Tools

Both the New York Times and the Washington Post are reporting that Israel has penetrated Kaspersky’s network and detected the Russian operation.

From the New York Times:

Israeli intelligence officers informed the NSA that, in the course of their Kaspersky hack, they uncovered evidence that Russian government hackers were using Kaspersky’s access to aggressively scan for American government classified programs and pulling any findings back to Russian intelligence systems. [Israeli intelligence] provided their NSA counterparts with solid evidence of the Kremlin campaign in the form of screenshots and other documentation, according to the people briefed on the events.

Kaspersky first noticed the Israeli intelligence operation in 2015.

The Washington Post writes about the NSA tools being on the home computer in the first place:

The employee, whose name has not been made public and is under investigation by federal prosecutors, did not intend to pass the material to a foreign adversary. “There wasn’t any malice,” said one person familiar with the case, who, like others interviewed, spoke on the condition of anonymity to discuss an ongoing case. “It’s just that he was trying to complete the mission, and he needed the tools to do it.

I don’t buy this. People with clearances are told over and over not to take classified material home with them. It’s not just mentioned occasionally; it’s a core part of the job.

More news articles.

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ISO Rejects NSA Encryption Algorithms

The ISO has decided not to approve two NSA-designed block encryption algorithms: Speck and Simon. It’s because the NSA is not trusted to put security ahead of surveillance:

A number of them voiced their distrust in emails to one another, seen by Reuters, and in written comments that are part of the process. The suspicions stem largely from internal NSA documents disclosed by Snowden that showed the agency had previously plotted to manipulate standards and promote technology it could penetrate. Budget documents, for example, sought funding to “insert vulnerabilities into commercial encryption systems.”

More than a dozen of the experts involved in the approval process for Simon and Speck feared that if the NSA was able to crack the encryption techniques, it would gain a “back door” into coded transmissions, according to the interviews and emails and other documents seen by Reuters.

“I don’t trust the designers,” Israeli delegate Orr Dunkelman, a computer science professor at the University of Haifa, told Reuters, citing Snowden’s papers. “There are quite a lot of people in NSA who think their job is to subvert standards. My job is to secure standards.”

I don’t trust the NSA, either.

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Proof that HMAC-DRBG has No Back Doors

New research: “Verified Correctness and Security of mbedTLS HMAC-DRBG,” by Katherine Q. Ye, Matthew Green, Naphat Sanguansin, Lennart Beringer, Adam Petcher, and Andrew W. Appel.

Abstract: We have formalized the functional specification of HMAC-DRBG (NIST 800-90A), and we have proved its cryptographic security — that its output is pseudorandom — using a hybrid game-based proof. We have also proved that the mbedTLS implementation (C program) correctly implements this functional specification. That proof composes with an existing C compiler correctness proof to guarantee, end-to-end, that the machine language program gives strong pseudorandomness. All proofs (hybrid games, C program verification, compiler, and their composition) are machine-checked in the Coq proof assistant. Our proofs are modular: the hybrid game proof holds on any implementation of HMAC-DRBG that satisfies our functional specification. Therefore, our functional specification can serve as a high-assurance reference.

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Alternatives to Government-Mandated Encryption Backdoors

Policy essay: “Encryption Substitutes,” by Andrew Keane Woods:

In this short essay, I make a few simple assumptions that bear mentioning at the outset. First, I assume that governments have good and legitimate reasons for getting access to personal data. These include things like controlling crime, fighting terrorism, and regulating territorial borders. Second, I assume that people have a right to expect privacy in their personal data. Therefore, policymakers should seek to satisfy both law enforcement and privacy concerns without unduly burdening one or the other. Of course, much of the debate over government access to data is about how to respect both of these assumptions. Different actors will make different trade-offs. My aim in this short essay is merely to show that regardless of where one draws this line — whether one is more concerned with ensuring privacy of personal information or ensuring that the government has access to crucial evidence — it would be shortsighted and counterproductive to draw that line with regard to one particular privacy technique and without regard to possible substitutes. The first part of the paper briefly characterizes the encryption debate two ways: first, as it is typically discussed, in stark, uncompromising terms; and second, as a subset of a broader problem. The second part summarizes several avenues available to law enforcement and intelligence agencies seeking access to data. The third part outlines the alternative avenues available to privacy-seekers. The availability of substitutes is relevant to the regulators but also to the regulated. If the encryption debate is one tool in a game of cat and mouse, the cat has other tools at his disposal to catch the mouse — and the mouse has other tools to evade the cat. The fourth part offers some initial thoughts on implications for the privacy debate.

Blog post.

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The US Senate Is Using Signal

The US Senate just approved Signal for staff use. Signal is a secure messaging app with no backdoor, and no large corporate owner who can be pressured to install a backdoor.

Susan Landau comments.

Maybe I’m being optimistic, but I think we just won the Crypto War. A very important part of the US government is prioritizing security over surveillance.

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Encryption Policy and Freedom of the Press

Interesting law journal article: “Encryption and the Press Clause,” by D. Victoria Barantetsky.

Abstract: Almost twenty years ago, a hostile debate over whether government could regulate encryption — later named the Crypto Wars — seized the country. At the center of this debate stirred one simple question: is encryption protected speech? This issue touched all branches of government percolating from Congress, to the President, and eventually to the federal courts. In a waterfall of cases, several United States Court of Appeals appeared to reach a consensus that encryption was protected speech under the First Amendment, and with that the Crypto Wars appeared to be over, until now.

Nearly twenty years later, the Crypto Wars have returned. Following recent mass shootings, law enforcement has once again questioned the legal protection for encryption and tried to implement “backdoor” techniques to access messages sent over encrypted channels. In the case, Apple v. FBI, the agency tried to compel Apple to grant access to the iPhone of a San Bernardino shooter. The case was never decided, but the legal arguments briefed before the court were essentially the same as they were two decades prior. Apple and amici supporting the company argued that encryption was protected speech.

While these arguments remain convincing, circumstances have changed in ways that should be reflected in the legal doctrines that lawyers use. Unlike twenty years ago, today surveillance is ubiquitous, and the need for encryption is no longer felt by a seldom few. Encryption has become necessary for even the most basic exchange of information given that most Americans share “nearly every aspect of their lives ­– from the mundane to the intimate” over the Internet, as stated in a recent Supreme Court opinion.

Given these developments, lawyers might consider a new justification under the Press Clause. In addition to the many doctrinal concerns that exist with protection under the Speech Clause, the
Press Clause is normatively and descriptively more accurate at protecting encryption as a tool for secure communication without fear of government surveillance. This Article outlines that framework by examining the historical and theoretical transformation of the Press Clause since its inception.

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Cryptkeeper Bug

The Linux encryption app Cryptkeeper has a rather stunning security bug: the single-character decryption key “p” decrypts everything:

The flawed version is in Debian 9 (Stretch), currently in testing, but not in Debian 8 (Jessie). The bug appears to be a result of a bad interaction with the encfs encrypted filesystem’s command line interface: Cryptkeeper invokes encfs and attempts to enter paranoia mode with a simulated ‘p’ keypress — instead, it sets passwords for folders to just that letter.

In 2013, I wrote an essay about how an organization might go about designing a perfect backdoor. This one seems much more like a bad mistake than deliberate action. It’s just too dumb, and too obvious. If anyone actually used Cryptkeeper, it would have been discovered long ago.

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WhatsApp Security Vulnerability

Back in March, Rolf Weber wrote about a potential vulnerability in the WhatsApp protocol that would allow Facebook to defeat perfect forward secrecy by forcibly change users’ keys, allowing it — or more likely, the government — to eavesdrop on encrypted messages.

It seems that this vulnerability is real:

WhatsApp has the ability to force the generation of new encryption keys for offline users, unbeknown to the sender and recipient of the messages, and to make the sender re-encrypt messages with new keys and send them again for any messages that have not been marked as delivered.

The recipient is not made aware of this change in encryption, while the sender is only notified if they have opted-in to encryption warnings in settings, and only after the messages have been re-sent. This re-encryption and rebroadcasting effectively allows WhatsApp to intercept and read users’ messages.

The security loophole was discovered by Tobias Boelter, a cryptography and security researcher at the University of California, Berkeley. He told the Guardian: “If WhatsApp is asked by a government agency to disclose its messaging records, it can effectively grant access due to the change in keys.”

The vulnerability is not inherent to the Signal protocol. Open Whisper Systems’ messaging app, Signal, the app used and recommended by whistleblower Edward Snowden, does not suffer from the same vulnerability. If a recipient changes the security key while offline, for instance, a sent message will fail to be delivered and the sender will be notified of the change in security keys without automatically resending the message.

WhatsApp’s implementation automatically resends an undelivered message with a new key without warning the user in advance or giving them the ability to prevent it.

Note that it’s an attack against current and future messages, and not something that would allow the government to reach into the past. In that way, it is no more troubling than the government hacking your mobile phone and reading your WhatsApp conversations that way.

An unnamed “WhatsApp spokesperson” said that they implemented the encryption this way for usability:

In WhatsApp’s implementation of the Signal protocol, we have a “Show Security Notifications” setting (option under Settings > Account > Security) that notifies you when a contact’s security code has changed. We know the most common reasons this happens are because someone has switched phones or reinstalled WhatsApp. This is because in many parts of the world, people frequently change devices and Sim cards. In these situations, we want to make sure people’s messages are delivered, not lost in transit.

He’s technically correct. This is not a backdoor. This really isn’t even a flaw. It’s a design decision that put usability ahead of security in this particular instance. Moxie Marlinspike, creator of Signal and the code base underlying WhatsApp’s encryption, said as much:

Under normal circumstances, when communicating with a contact who has recently changed devices or reinstalled WhatsApp, it might be possible to send a message before the sending client discovers that the receiving client has new keys. The recipient’s device immediately responds, and asks the sender to reencrypt the message with the recipient’s new identity key pair. The sender displays the “safety number has changed” notification, reencrypts the message, and delivers it.

The WhatsApp clients have been carefully designed so that they will not re-encrypt messages that have already been delivered. Once the sending client displays a “double check mark,” it can no longer be asked to re-send that message. This prevents anyone who compromises the server from being able to selectively target previously delivered messages for re-encryption.

The fact that WhatsApp handles key changes is not a “backdoor,” it is how cryptography works. Any attempt to intercept messages in transmit by the server is detectable by the sender, just like with Signal, PGP, or any other end-to-end encrypted communication system.

The only question it might be reasonable to ask is whether these safety number change notifications should be “blocking” or “non-blocking.” In other words, when a contact’s key changes, should WhatsApp require the user to manually verify the new key before continuing, or should WhatsApp display an advisory notification and continue without blocking the user.

Given the size and scope of WhatsApp’s user base, we feel that their choice to display a non-blocking notification is appropriate. It provides transparent and cryptographically guaranteed confidence in the privacy of a user’s communication, along with a simple user experience. The choice to make these notifications “blocking” would in some ways make things worse. That would leak information to the server about who has enabled safety number change notifications and who hasn’t, effectively telling the server who it could MITM transparently and who it couldn’t; something that WhatsApp considered very carefully.

How serious this is depends on your threat model. If you are worried about the US government — or any other government that can pressure Facebook — snooping on your messages, then this is a small vulnerability. If not, then it’s nothing to worry about.

Slashdot thread. Hacker News thread. BoingBoing post. More here.

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Encryption Working Group Annual Report from the US House of Representatives

The Encryption Working Group of the House Judiciary Committee and the House Energy and Commerce Committee has released its annual report.

Observation #1: Any measure that weakens encryption works against the national interest.

Observation #2: Encryption technology is a global technology that is widely and increasingly available around the world.

Observation #3: The variety of stakeholders, technologies, and other factors create different and divergent challenges with respect to encryption and the “going dark” phenomenon, and therefore there is no one-size-fits-all solution to the encryption challenge.

Observation #4: Congress should foster cooperation between the law enforcement community and technology companies.

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