Qredit Qards? University of Vienna Researchers Use Quantum Physics to Secure Digital Payments

Insider Summary

• The University of Vienna research team has demonstrated how the quantum properties of light particles or photons can ensure unconditional security for digital payments.
• The researchers demonstrated that each transaction cannot be duplicated or routed by malicious parties, and that sensitive user data remains private.
• The findings are published in Nature Communications.
• Image: An artistic image of a digital payment secured by quantum technology (Christine Schiansky)

PRESS RELEASE — Have you ever been forced to enter sensitive payment data on an unknown merchant’s website? Are you willing to hand over your credit card data or passwords to untrustworthy hands? Scientists from the University of Vienna have now designed an unconditionally secure shopping system in such settings, combining modern cryptographic techniques with the fundamental properties of quantum light. The demonstration of such “quantum digital payments” in a realistic environment has just been published Nature Communications.

Digital payments have replaced physical paper money in many aspects of our daily lives. Similar to paper money, paper money needs to be easy to use, unique, tamper-resistant and untraceable, but also resistant to digital attackers and data breaches. In today’s payments ecosystem, sensitive customer data is replaced with random sequences of numbers, and the uniqueness of each transaction is guaranteed by classical cryptographic methods or codes. However, adversaries and merchants with powerful computing resources can decode this and recover customers’ personal data, and for example make payments on their behalf.

A research team led by Prof. Philip Walther of the University of Vienna has shown how the quantum nature of light particles or photons can ensure unconditional security for digital payments. In an experiment, researchers have shown that transactions cannot be duplicated or routed by malicious parties, and that sensitive user data remains private.

“I am deeply impressed how the quantum nature of light can be used to protect new applications such as digital payments that are relevant in our everyday lives,” said Tobias Guggemos.

To enable absolutely secure digital payments, scientists are replacing classical cryptographic techniques with quantum protocols that exploit single photons. During a classic digital payment transaction, the client shares a classic code – called a cryptogram – with its payment provider (eg a bank or credit card company).

This cryptogram is then passed between the customer, the merchant, and the payment provider. In the demonstrated quantum protocol, this cryptogram is generated by having a payment provider send a specially prepared single photon to the client.

For the payment procedure, the client measures these photons where the measurement setting depends on transaction parameters. Since the quantum light state cannot be copied, a transaction can only be executed once. This, together with the fact that any intentional deviation from payment changes the measurement results, which are verified by the payment provider, making these digital payments unconditionally secure.

Researchers have successfully implemented quantum digital payments via a 641m urban fiber-optic link, connecting two university buildings in the center of Vienna. Today’s digital payments operate within seconds. “Currently, our protocol requires several minutes of quantum communication to complete a transaction. This is to guarantee safety in the face of noise and loss,” said Peter Schiansky, first author of the paper. “However, this time limit is purely technological” adds Matthieu Bozzio, who is confident that “we will see that quantum digital payments reach practical performance in the near future”.