Entries Tagged "cryptography"

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Indistinguishability Obfuscation

Quanta magazine recently published a breathless article on indistinguishability obfuscation — calling it the “‘crown jewel’ of cryptography” — and saying that it had finally been achieved, based on a recently published paper. I want to add some caveats to the discussion.

Basically, obfuscation makes a computer program “unintelligible” by performing its functionality. Indistinguishability obfuscation is more relaxed. It just means that two different programs that perform the same functionality can’t be distinguished from each other. A good definition is in this paper.

This is a pretty amazing theoretical result, and one to be excited about. We can now do obfuscation, and we can do it using assumptions that make real-world sense. The proofs are kind of ugly, but that’s okay — it’s a start. What it means in theory is that we have a fundamental theoretical result that we can use to derive a whole bunch of other cryptographic primitives.

But — and this is a big one — this result is not even remotely close to being practical. We’re talking multiple days to perform pretty simple calculations, using massively large blocks of computer code. And this is likely to remain true for a very long time. Unless researchers increase performance by many orders of magnitude, nothing in the real world will make use of this work anytime soon.

But but, consider fully homomorphic encryption. It, too, was initially theoretically interesting and completely impractical. And now, after decades of work, it seems to be almost just-barely maybe approaching practically useful. This could very well be on the same trajectory, and perhaps in twenty to thirty years we will be celebrating this early theoretical result as the beginning of a new theory of cryptography.

Posted on November 23, 2020 at 6:04 AMView Comments


DiceKeys is a physical mechanism for creating and storing a 192-bit key. The idea is that you roll a special set of twenty-five dice, put them into a plastic jig, and then use an app to convert those dice into a key. You can then use that key for a variety of purposes, and regenerate it from the dice if you need to.

This week Stuart Schechter, a computer scientist at the University of California, Berkeley, is launching DiceKeys, a simple kit for physically generating a single super-secure key that can serve as the basis for creating all the most important passwords in your life for years or even decades to come. With little more than a plastic contraption that looks a bit like a Boggle set and an accompanying web app to scan the resulting dice roll, DiceKeys creates a highly random, mathematically unguessable key. You can then use that key to derive master passwords for password managers, as the seed to create a U2F key for two-factor authentication, or even as the secret key for cryptocurrency wallets. Perhaps most importantly, the box of dice is designed to serve as a permanent, offline key to regenerate that master password, crypto key, or U2F token if it gets lost, forgotten, or broken.


Schechter is also building a separate app that will integrate with DiceKeys to allow users to write a DiceKeys-generated key to their U2F two-factor authentication token. Currently the app works only with the open-source SoloKey U2F token, but Schechter hopes to expand it to be compatible with more commonly used U2F tokens before DiceKeys ship out. The same API that allows that integration with his U2F token app will also allow cryptocurrency wallet developers to integrate their wallets with DiceKeys, so that with a compatible wallet app, DiceKeys can generate the cryptographic key that protects your crypto coins too.

Here’s the DiceKeys website and app. Here’s a short video demo. Here’s a longer SOUPS talk.

Preorder a set here.

Note: I am an adviser on the project.

Another news article. Slashdot thread. Hacker News thread. Reddit thread.

Posted on August 24, 2020 at 6:23 AMView Comments

Update on NIST's Post-Quantum Cryptography Program

NIST has posted an update on their post-quantum cryptography program:

After spending more than three years examining new approaches to encryption and data protection that could defeat an assault from a quantum computer, the National Institute of Standards and Technology (NIST) has winnowed the 69 submissions it initially received down to a final group of 15. NIST has now begun the third round of public review. This “selection round” will help the agency decide on the small subset of these algorithms that will form the core of the first post-quantum cryptography standard.


For this third round, the organizers have taken the novel step of dividing the remaining candidate algorithms into two groups they call tracks. The first track contains the seven algorithms that appear to have the most promise.

“We’re calling these seven the finalists,” Moody said. “For the most part, they’re general-purpose algorithms that we think could find wide application and be ready to go after the third round.”

The eight alternate algorithms in the second track are those that either might need more time to mature or are tailored to more specific applications. The review process will continue after the third round ends, and eventually some of these second-track candidates could become part of the standard. Because all of the candidates still in play are essentially survivors from the initial group of submissions from 2016, there will also be future consideration of more recently developed ideas, Moody said.

“The likely outcome is that at the end of this third round, we will standardize one or two algorithms for encryption and key establishment, and one or two others for digital signatures,” he said. “But by the time we are finished, the review process will have been going on for five or six years, and someone may have had a good idea in the interim. So we’ll find a way to look at newer approaches too.”

Details are here. This is all excellent work, and exemplifies NIST at its best. The quantum-resistant algorithms will be standardized far in advance of any practical quantum computer, which is how we all want this sort of thing to go.

Posted on July 24, 2020 at 6:36 AMView Comments

NSA on Securing VPNs

The NSA’s Cybersecurity Directorate — that’s the part that’s supposed to work on defense — has released two documents (a full and an abridged version) on securing virtual private networks. Some of it is basic, but it contains good information.

Maintaining a secure VPN tunnel can be complex and requires regular maintenance. To maintain a secure VPN, network administrators should perform the following tasks on a regular basis:

  • Reduce the VPN gateway attack surface
  • Verify that cryptographic algorithms are Committee on National Security Systems Policy (CNSSP) 15-compliant
  • Avoid using default VPN settings
  • Remove unused or non-compliant cryptography suites
  • Apply vendor-provided updates (i.e. patches) for VPN gateways and clients

Posted on July 15, 2020 at 9:29 AMView Comments

Another Story of Bad 1970s Encryption

This one is from the Netherlands. It seems to be clever cryptanalysis rather than a backdoor.

The Dutch intelligence service has been able to read encrypted communications from dozens of countries since the late 1970s thanks to a microchip, according to research by de Volkskrant on Thursday. The Netherlands could eavesdrop on confidential communication from countries such as Iran, Egypt and Saudi Arabia.

Philips, together with Siemens, built an encryption machine in the late 1970s. The device, the Aroflex, was used for secret communication between NATO allies. In addition, the companies also wanted to market the T1000CA, a commercial variant of the Aroflex with less strong cryptography.

The Volkskrant investigation shows that the Ministry of Foreign Affairs and the Marine Intelligence Service (MARID) cracked the cryptography of this device before it was launched. Philips helped the ministry and the intelligence service.

Normally it would take at least a month and a half to crack the T1000CA encryption. “Too long to get useful information from intercepted communication,” the newspaper writes. But MARID employees, together with Philips, succeeded in accelerating this 2.500 times by developing a special microchip.

The T1000CA was then sold to numerous non-NATO countries, including the Middle East and Asia. These countries could then be overheard by the Dutch intelligence services for years.

The 1970s was a decade of really bad commercial cryptography. DES, in 1975, was an improvement with its 56-bit key. I’m sure there are lots of these stories.

Here’s more about the Aroflex. And here’s what I think is the original Dutch story.

Posted on April 21, 2020 at 6:22 AMView Comments

RSA-250 Factored

RSA-250 has been factored.

This computation was performed with the Number Field Sieve algorithm,
using the open-source CADO-NFS software.

The total computation time was roughly 2700 core-years, using Intel Xeon Gold 6130 CPUs as a reference (2.1GHz):

RSA-250 sieving: 2450 physical core-years
RSA-250 matrix: 250 physical core-years

The computation involved tens of thousands of machines worldwide, and was completed in a few months.

News article. On the factoring challenges.

Posted on April 8, 2020 at 6:37 AMView Comments


Prepare for another attack on encryption in the U.S. The EARN-IT Act purports to be about protecting children from predation, but it’s really about forcing the tech companies to break their encryption schemes:

The EARN IT Act would create a “National Commission on Online Child Sexual Exploitation Prevention” tasked with developing “best practices” for owners of Internet platforms to “prevent, reduce, and respond” to child exploitation. But far from mere recommendations, those “best practices” would be approved by Congress as legal requirements: if a platform failed to adhere to them, it would lose essential legal protections for free speech.

It’s easy to predict how Attorney General William Barr would use that power: to break encryption. He’s said over and over that he thinks the “best practice” is to force encrypted messaging systems to give law enforcement access to our private conversations. The Graham-Blumenthal bill would finally give Barr the power to demand that tech companies obey him or face serious repercussions, including both civil and criminal liability. Such a demand would put encryption providers like WhatsApp and Signal in an awful conundrum: either face the possibility of losing everything in a single lawsuit or knowingly undermine their users’ security, making all of us more vulnerable to online criminals.

Matthew Green has a long explanation of the bill and its effects:

The new bill, out of Lindsey Graham’s Judiciary committee, is designed to force providers to either solve the encryption-while-scanning problem, or stop using encryption entirely. And given that we don’t yet know how to solve the problem — and the techniques to do it are basically at the research stage of R&D — it’s likely that “stop using encryption” is really the preferred goal.

EARN IT works by revoking a type of liability called Section 230 that makes it possible for providers to operate on the Internet, by preventing the provider for being held responsible for what their customers do on a platform like Facebook. The new bill would make it financially impossible for providers like WhatsApp and Apple to operate services unless they conduct “best practices” for scanning their systems for CSAM.

Since there are no “best practices” in existence, and the techniques for doing this while preserving privacy are completely unknown, the bill creates a government-appointed committee that will tell technology providers what technology they have to use. The specific nature of the committee is byzantine and described within the bill itself. Needless to say, the makeup of the committee, which can include as few as zero data security experts, ensures that end-to-end encryption will almost certainly not be considered a best practice.

So in short: this bill is a backdoor way to allow the government to ban encryption on commercial services. And even more beautifully: it doesn’t come out and actually ban the use of encryption, it just makes encryption commercially infeasible for major providers to deploy, ensuring that they’ll go bankrupt if they try to disobey this committee’s recommendations.

It’s the kind of bill you’d come up with if you knew the thing you wanted to do was unconstitutional and highly unpopular, and you basically didn’t care.

Another criticism of the bill. Commentary by EPIC. Kinder analysis.

Sign a petition against this act.

Posted on March 13, 2020 at 6:20 AMView Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.