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Article Released Thu-31st-May-2018 10:26 GMT
Contact: Alison Hadley Institution: IOP Publishing
 Quantum is key to securing blockchain, say Russian researchers

Although blockchain is traditionally seen as secure, it is vulnerable to attack from quantum computers.

Now, a team of Russian researchers has developed a solution to the quantum-era blockchain challenge, using quantum key distribution (QKD).

Writing in the journal Quantum Science and Technology, the researchers set out a quantum-safe blockchain platform that uses QKD to achieve secure authentication.

The blockchain is a distributed ledger platform that allows consensus in a large decentralized network of parties who do not trust each other. Transactions are accountable and transparent, making it useful for a variety of applications from smart contracts and finance, to manufacturing and healthcare. One of the most prominent applications of blockchains is cryptocurrencies, such as Bitcoin.

Lead author Dr Evgeniy Kiktenko, from the Russian Quantum Center, Moscow, said: “Blockchain is promising for a wide range of applications. But current platforms rely on digital signatures, which are vulnerable to attacks by quantum computers. This also applies to the cryptographic hash functions used in preparing new blocks, meaning those with access to quantum computation would have an unfair advantage in procuring mining rewards, such as Bitcoins. These risks are significant – it is predicted that 10 percent of global GDP will be stored on blockchains or blockchain-related technology by 2025.

To overcome these risks, the researchers developed a blockchain platform combining original state-machine replication – a general method for implementing a fault-tolerant service by replicating servers and coordinating client interactions with server replicas – without use of digital signatures, and QKD for providing authentication

They then ran an experiment to test its capability in an urban QKD network.

Co-lead author Dr Aleksey Fedorov, from the Russian Quantum Center, said: “Using QKD for blockchains may appear counterintuitive, as QKD networks rely on trust among nodes, whereas many blockchains lack such trust. More specifically, one may argue that QKD cannot be used for authentication because it requires an authenticated classical channel for operation itself.

“However, each QKD communication session generates a large amount of shared secret data, part of which can be used for authentication in subsequent sessions. Therefore, a small amount of 'seed' secret key that the parties share before their first QKD session ensures their secure authentication for all future communication. This means QKD can be used in lieu of classical digital signatures.”

In addition to using QKD for authentication, the researchers redefined the protocol of adding new blocks in a different way from modern cryptocurrencies. Rather than concentrating the development of new blocks in the hands of individual miners, they employed the information-theoretically secure broadcast protocol, where all nodes reach an agreement about a new block on equal terms.

Co-lead author Prof. Alexander Lvovsky said: “A crucial advantage of our blockchain protocol is its ability to maintain transparency and integrity of transactions against attacks with quantum algorithms. Our results therefore open up possibilities for realising scalable quantum-safe blockchain platforms. If realised, such a blockchain platform can limit economic and social risks from imminent breakthroughs in quantum computation technology.”



The final version of ‘Quantum-secured blockchain’ by Evgeniy Kiktenko et al (QST volume 3, issue 3, article 035004) will be available at 00.00 BST on Thursday May 31 at the link below. DOI 10.1088/2058-9565/aabc6b

For an advance copy of the paper, further information, or spokesperson contact details, please contact: Simon Davies, Senior PR Officer, IOP Publishing Tel 0117 930 1110 Email

About Quantum Science and Technology

QST is a multidisciplinary, high impact journal devoted to publishing research of the highest quality and significance, covering the science and application of all quantum-enabled technologies.

About IOP Publishing
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About the Institute of Physics

The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application. We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications. Visit us at the website (link below). Follow IOP on Twitter via @PhysicsNews

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