Other Budapest Meshtastic users’ devices relayed some of the researchers’ encrypted radio messages, but the contents stayed unreadable without the right key. The successful public-network test used encryption keys created through quantum key distribution, not a new kind of quantum radio.
Researchers from the HUN-REN Wigner Research Centre for Physics and ELTE’s Faculty of Informatics carried out the demonstration on October 29, 2026, as part of the QCIHungary project. According to HUN-REN’s account, they believe this was the world’s first use of a quantum-distributed key to encrypt Meshtastic messages.
The radio traffic traveled over an existing, publicly accessible network. Meshtastic uses LoRa-based radio communication, which consumes little power and can provide a range of several kilometers, potentially even tens of kilometers, without central infrastructure or mobile service. Its devices form a mesh network, forwarding messages between one another. That can make it useful in the field, at events, or wherever reliable internet or mobile coverage is missing.
Quantum key distribution, or QKD, supplied the secret key shared by the two researchers. It establishes a secret key between two parties, with security grounded in the laws of physics rather than the difficulty of solving mathematical problems. In principle, even future quantum computers cannot break that key, and attempts to eavesdrop on its distribution can be detected. These are properties of the key-distribution process; the radios themselves do not transmit quantum signals.
To prepare the test, one researcher requested a fresh key from the quantum key-distribution equipment at Pro-M Zrt.’s Victor Hugo Street site and used it to create the encrypted channel. Their colleague used the key’s identifier to retrieve the same key from the equipment at Wigner. Both could then configure their radios with the same protection.
Testing took place in ordinary city conditions. One researcher set off from Szent István körút and the other from Széll Kálmán tér, heading toward each other. Between 11:21 and 11:39, they exchanged several encrypted messages, eventually communicating successfully from the two ends of Margaret Bridge.
One message read, “Physics enlightens the world!” The reply was “Indeed!” They continued testing while moving, including from a bus, and the system still worked.
Measurements indicated that the public mesh carried traffic as usual. The practical result was quantum-distributed keys protecting messages sent over an existing, accessible radio technology outside an isolated laboratory. The demonstration points toward possible practical forms of secure communication without requiring the underlying mesh to become a quantum network.
QCIHungary is Hungary’s contribution to the EU’s European Quantum Communication Infrastructure initiative, EuroQCI, which aims to build infrastructure protected by quantum communication across the European Union. The Hungarian consortium consists of Pro-M Zrt., the Budapest University of Technology and Economics, ELTE’s Faculty of Informatics, and the HUN-REN Wigner Research Centre for Physics.
Supported by the Digital Europe Programme, the project is laying the foundations for a quantum-communication backbone connecting Budapest with Győr and Szeged.
