Entries Tagged "quantum cryptography"

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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

GCHQ on Quantum Key Distribution

The UK’s GCHQ delivers a brutally blunt assessment of quantum key distribution:

QKD protocols address only the problem of agreeing keys for encrypting data. Ubiquitous on-demand modern services (such as verifying identities and data integrity, establishing network sessions, providing access control, and automatic software updates) rely more on authentication and integrity mechanisms — such as digital signatures — than on encryption.

QKD technology cannot replace the flexible authentication mechanisms provided by contemporary public key signatures. QKD also seems unsuitable for some of the grand future challenges such as securing the Internet of Things (IoT), big data, social media, or cloud applications.

I agree with them. It’s a clever idea, but basically useless in practice. I don’t even think it’s anything more than a niche solution in a world where quantum computers have broken our traditional public-key algorithms.

Read the whole thing. It’s short.

Posted on August 1, 2018 at 2:07 PMView Comments

Quantum Tokens for Digital Signatures

This paper wins “best abstract” award: “Quantum Tokens for Digital Signatures,” by Shalev Ben David and Or Sattath:

Abstract: The fisherman caught a quantum fish. “Fisherman, please let me go,” begged the fish, “and I will grant you three wishes.” The fisherman agreed. The fish gave the fisherman a quantum computer, three quantum signing tokens and his classical public key.

The fish explained: “to sign your three wishes, use the tokenized signature scheme on this quantum computer, then show your valid signature to the king, who owes me a favor.”

The fisherman used one of the signing tokens to sign the document “give me a castle!” and rushed to the palace. The king executed the classical verification algorithm using the fish’s public key, and since it was valid, the king complied.

The fisherman’s wife wanted to sign ten wishes using their two remaining signing tokens. The fisherman did not want to cheat, and secretly sailed to meet the fish. “Fish, my wife wants to sign ten more wishes.”

But the fish was not worried: “I have learned quantum cryptography following the previous story (The Fisherman and His Wife by the brothers Grimm). The quantum tokens are consumed during the signing. Your polynomial wife cannot even sign four wishes using the three signing tokens I gave you.”

“How does it work?” wondered the fisherman.

“Have you heard of quantum money? These are quantum states which can be easily verified but are hard to copy. This tokenized quantum signature scheme extends Aaronson and Christiano’s quantum money scheme, which is why the signing tokens cannot be copied.”

“Does your scheme have additional fancy properties?” the fisherman asked.

“Yes, the scheme has other security guarantees: revocability, testability and everlasting security. Furthermore, if you’re at the sea and your quantum phone has only classical reception, you can use this scheme to transfer the value of the quantum money to shore,” said the fish, and swam his way.

Posted on October 6, 2016 at 7:03 AMView Comments

NSA Plans for a Post-Quantum World

Quantum computing is a novel way to build computers — one that takes advantage of the quantum properties of particles to perform operations on data in a very different way than traditional computers. In some cases, the algorithm speedups are extraordinary.

Specifically, a quantum computer using something called Shor’s algorithm can efficiently factor numbers, breaking RSA. A variant can break Diffie-Hellman and other discrete log-based cryptosystems, including those that use elliptic curves. This could potentially render all modern public-key algorithms insecure. Before you panic, note that the largest number to date that has been factored by a quantum computer is 143. So while a practical quantum computer is still science fiction, it’s not stupid science fiction.

(Note that this is completely different from quantum cryptography, which is a way of passing bits between two parties that relies on physical quantum properties for security. The only thing quantum computation and quantum cryptography have to do with each other is their first words. It is also completely different from the NSA’s QUANTUM program, which is its code name for a packet-injection system that works directly in the Internet backbone.)

Practical quantum computation doesn’t mean the end of cryptography. There are lesser-known public-key algorithms such as McEliece and lattice-based algorithms that, while less efficient than the ones we use, are currently secure against a quantum computer. And quantum computation only speeds up a brute-force keysearch by a factor of a square root, so any symmetric algorithm can be made secure against a quantum computer by doubling the key length.

We know from the Snowden documents that the NSA is conducting research on both quantum computation and quantum cryptography. It’s not a lot of money, and few believe that the NSA has made any real advances in theoretical or applied physics in this area. My guess has been that we’ll see a practical quantum computer within 30 to 40 years, but not much sooner than that.

This all means that now is the time to think about what living in a post-quantum world would be like. NIST is doing its part, having hosted a conference on the topic earlier this year. And the NSA announced that it is moving towards quantum-resistant algorithms.

Earlier this week, the NSA’s Information Assurance Directorate updated its list of Suite B cryptographic algorithms. It explicitly talked about the threat of quantum computers:

IAD will initiate a transition to quantum resistant algorithms in the not too distant future. Based on experience in deploying Suite B, we have determined to start planning and communicating early about the upcoming transition to quantum resistant algorithms. Our ultimate goal is to provide cost effective security against a potential quantum computer. We are working with partners across the USG, vendors, and standards bodies to ensure there is a clear plan for getting a new suite of algorithms that are developed in an open and transparent manner that will form the foundation of our next Suite of cryptographic algorithms.

Until this new suite is developed and products are available implementing the quantum resistant suite, we will rely on current algorithms. For those partners and vendors that have not yet made the transition to Suite B elliptic curve algorithms, we recommend not making a significant expenditure to do so at this point but instead to prepare for the upcoming quantum resistant algorithm transition.

Suite B is a family of cryptographic algorithms approved by the NSA. It’s all part of the NSA’s Cryptographic Modernization Program. Traditionally, NSA algorithms were classified and could only be used in specially built hardware modules. Suite B algorithms are public, and can be used in anything. This is not to say that Suite B algorithms are second class, or breakable by the NSA. They’re being used to protect US secrets: “Suite A will be used in applications where Suite B may not be appropriate. Both Suite A and Suite B can be used to protect foreign releasable information, US-Only information, and Sensitive Compartmented Information (SCI).”

The NSA is worried enough about advances in the technology to start transitioning away from algorithms that are vulnerable to a quantum computer. Does this mean that the agency is close to a working prototype in their own classified labs? Unlikely. Does this mean that they envision practical quantum computers sooner than my 30-to-40-year estimate? Certainly.

Unlike most personal and corporate applications, the NSA routinely deals with information it wants kept secret for decades. Even so, we should all follow the NSA’s lead and transition our own systems to quantum-resistant algorithms over the next decade or so — possibly even sooner.

The essay previously appeared on Lawfare.

EDITED TO ADD: The computation that factored 143 also accidentally “factored much larger numbers such as 3599, 11663, and 56153, without the awareness of the authors of that work,” which shows how weird this all is.

EDITED TO ADD: Seems that I need to be clearer: I do not stand by my 30-40-year prediction. The NSA is acting like practical quantum computers will exist long before then, and I am deferring to their expertise.

Posted on August 21, 2015 at 12:36 PMView Comments

Successful Attack Against a Quantum Cryptography System

Clever:

Quantum cryptography is often touted as being perfectly secure. It is based on the principle that you cannot make measurements of a quantum system without disturbing it. So, in theory, it is impossible for an eavesdropper to intercept a quantum encryption key without disrupting it in a noticeable way, triggering alarm bells.

Vadim Makarov at the Norwegian University of Science and Technology in Trondheim and his colleagues have now cracked it. “Our hack gave 100% knowledge of the key, with zero disturbance to the system,” he says.

[…]

The cunning part is that while blinded, Bob’s detector cannot function as a ‘quantum detector’ that distinguishes between different quantum states of incoming light. However, it does still work as a ‘classical detector’ ­ recording a bit value of 1 if it is hit by an additional bright light pulse, regardless of the quantum properties of that pulse.

That means that every time Eve intercepts a bit value of 1 from Alice, she can send a bright pulse to Bob, so that he also receives the correct signal, and is entirely unaware that his detector has been sabotaged. There is no mismatch between Eve and Bob’s readings because Eve sends Bob a classical signal, not a quantum one. As quantum cryptographic rules no longer apply, no alarm bells are triggered, says Makarov.

“We have exploited a purely technological loophole that turns a quantum cryptographic system into a classical system, without anyone noticing,” says Makarov.

Makarov and his team have demonstrated that the hack works on two commercially available systems: one sold by ID Quantique (IDQ), based in Geneva, Switzerland, and one by MagiQ Technologies, based in Boston, Massachusetts. “Once I had the systems in the lab, it took only about two months to develop a working hack,” says Makarov.

Just because something is secure in theory doesn’t mean it’s secure in practice. Or, to put it more cleverly: in theory, theory and practice are the same; but in practice, they’re very different.

The paper is here.

Posted on September 2, 2010 at 1:46 PMView Comments

Location-Based Quantum Encryption

Location-based encryption — a system by which only a recipient in a specific location can decrypt the message — fails because location can be spoofed. Now a group of researchers has solved the problem in a quantum cryptography setting:

The research group has recently shown that if one sends quantum bits — the quantum equivalent of a bit — instead of only classical bits, a secure protocol can be obtained such that the location of a device cannot be spoofed. This, in turn, leads to a key-exchange protocol based solely on location.

The core idea behind the protocol is the “no-cloning” principle of quantum mechanics. By making a device give the responses of random challenges to several verifiers, the protocol ensures that multiple colluding devices cannot falsely prove any location. This is because an adversarial device can either store the quantum state of the challenge or send it to a colluding adversary, but not both.

Don’t expect this in a product anytime soon. Quantum cryptography is mostly theoretical and almost entirely laboratory-only. But as research, it’s great stuff. Paper here.

Posted on August 3, 2010 at 6:25 AMView Comments

Quantum Cryptography Cracked

Impressive:

This presentation will show the first experimental implementation of an eavesdropper for quantum cryptosystem. Although quantum cryptography has been proven unconditionally secure, by exploiting physical imperfections (detector vulnerability) we have successfully built an intercept-resend attack and demonstrated eavesdropping under realistic conditions on an installed quantum key distribution line. The actual eavesdropping hardware we have built will be shown during the conference.

While I am very interested in quantum cryptography, I have never been optimistic about its practicality. And it’s always interesting to see provably secure cryptosystems broken.

Posted on December 30, 2009 at 6:04 AMView Comments

Sidebar photo of Bruce Schneier by Joe MacInnis.