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A quantum computer at IBM’s Thomas J. Watson Research Center.

Credit: Connie Zhou for IBM

Topics: Computer Science, Cryptography, Cybersecurity, Quantum Computer

A team of researchers in China has unveiled a technique that — theoretically — could crack the most commonly used types of digital privacy using a rudimentary quantum computer.

The technique worked in a small-scale demonstration, the researchers report, but other experts are skeptical that the procedure could scale up to beat ordinary computers at the task. Still, they Are quantum computers about to break online privacy. Davide Castelvecchi, Naturewarn that the paper, posted late last month on the arXiv repository¹, is a reminder of the vulnerability of online privacy.

Quantum computers are known to be a potential threat to current encryption systems. However, the technology is still in its infancy, and researchers typically estimate that it will be many years until it can be faster than ordinary computers at cracking cryptographic keys.

Researchers realized in the 1990s that quantum computers could exploit peculiarities of physics to perform tasks that seem to be beyond the reach of ‘classical’ computers. Peter Shor, a mathematician now at the Massachusetts Institute of Technology in Cambridge, showed in 1994² how to apply the phenomena of quantum superposition and interference to factoring integer numbers into primes — the integers that cannot be further divided without a remainder.

Are quantum computers about to break online privacy? Davide Castelvecchi, Nature

Quantum physics experiment has demonstrated an important step toward achieving quantum cryptography among many users, an essential requirement for a secure quantum Internet. Credit: ÖAW and Klaus Pichler Getty Images

Party line: the new protocol allows 10 parties to share information securely. (Courtesy: University of Witwatersrand)

Topics: Cryptography, Quantum Computer, Quantum Mechanics

A “quantum secret sharing” scheme that allows 10 parties to share information securely – the highest number so far – has been developed and demonstrated by researchers in South Africa. The protocol involves each party performing quantum operations on the photon without measuring its state and the team says it could help increase both the rate at which data is shared on secure quantum networks and how many parties can be involved in the sharing.

In the original quantum key distribution (QKD) protocol, two parties, known as Alice and Bob, communicate by exchanging photons polarized in one of two possible bases over an untrusted link, each varying the polarization basis of his or her transmitter or receiver randomly. At the end of the transmission, Alice and Bob reveal to each other which basis they used to measure the photons sent and received, but not the result of the measurements.  Alice and Bob then announce their results for a sample of the photons in which they measured in the same polarization basis, to check that the emitted polarization always agrees with the received one. If it does, they can use the remaining photons that they measured in the same basis to form a secure cryptography key that allows them to communicate securely using conventional telecoms technology. A third party that intercepts the photons inevitably disturbs their state, so some of Alice and Bob’s measurements disagree and they know the line is bugged.

‘Quantum secret sharing’ scheme allows 10 parties to communicate securely, Physics World

This artist’s conception of threshold cryptography shows a lock that can only be opened by three people working together. When the threshold cryptosystem receives a request to process information with a secret key, it initially splits the key into shares and sends them to the entire group, each share to a different participant. The three people must agree to work together and also perform their own secret operations on the incoming message. From these actions, each person uses their share key — represented by the three colored circles — to process the message, and then sends the result back to the system. Only the combination of all three partial results can open the lock, reducing the likelihood that a single corrupt party could compromise the system.

Topics: Cryptography, Computer Science, Electrical Engineering, NIST

A new publication by cryptography experts at the National Institute of Standards and Technology (NIST) proposes the direction the technical agency will take to develop a more secure approach to encryption. This approach, called threshold cryptography, could overcome some of the limitations of conventional methods for protecting sensitive transactions and data.

The document, released today in a final version as NIST Roadmap Toward Criteria for Threshold Schemes for Cryptographic Primitives (NISTIR 8214A), offers an outline for developing a new way to implement the cryptographic tools that developers use to secure their systems. Its authors are inviting the cryptography community to collaborate with them on NIST’s budding Threshold Cryptography project, which in part seeks to ensure that threshold implementations are interoperable.

“We are kicking the threshold cryptography development effort into high gear,” said Apostol Vassilev, a NIST computer scientist. “Over the coming months, the Threshold Cryptography project will be engaging with the public to define criteria for this work. We want to get feedback from the community so we can consider a variety of threshold schemes and standardization paths.”

Threshold cryptography takes its name from the idea that individual keyholders cannot open a lock on their own, as is common in conventional cryptography. Instead, out of a group of keyholders, there must be a minimum number of them — a “threshold” number — working together to open the lock. In practice, this lock is an electronic cryptosystem that protects confidential information, such as a bank account number or an authorization to transfer money from that account.

NIST Kick-Starts ‘Threshold Cryptography’ Development Effort