A new chapter in quantum encryption

Researchers from the University of California (Santa Barbara), and UCLA have introduced a universal construction for Unclonable Encryption with a classical key — the first scheme that simultaneously achieves efficient encryption and decryption and exponentially small unclonable-indistinguishability advantage.

Unclonable encryption is a branch of quantum cryptography that leverages the no-cloning principle of quantum mechanics. In the classical world, if an adversary intercepts an encrypted message and later obtains the key, they can decrypt it. In the quantum world, however, the ciphertext exists as a quantum state — a collection of qubits — which cannot be copied. The key remains an ordinary classical bit string. Thus, even if the secret key is later revealed, only the party in possession of the original quantum state can recover the message.

The idea of quantum unclonable encryption was first proposed by Daniel Gottesman back in 2003. However, his construction required the key to be as long as the message. For the next 20 years, researchers tried to create an efficient unclonable encryption scheme in which encryption and decryption times would not grow exponentially with the message size. However, all existing schemes were either inefficient, relied on mathematical abstractions that do not exist in reality (such as a quantum random oracle), or provided insufficient protection.

What did the authors do? Another group of researchers in 2026 introduced a new encryption construction, but their scheme only provided inverse-polynomial security and was verified only for small parameters — a full proof of negligible security remained elusive. The authors of the new paper took the same construction and built a scheme that combines three properties previously considered incompatible: • information-theoretically secure — even with unlimited computing power, the probability of a successful attack approaches zero; • exfficient — encryption and decryption times grow polynomially rather than exponentially; • in the plain model — the scheme works without idealized assumptions or mathematical abstractions.

The news is notable not only for the result itself, but also for how it was achieved. The construction and the main ideas behind the proof were generated entirely by the Codex based on GPT 5.6 Sol Ultra. The AI found an alternative line of reasoning for solving an exceptionally difficult mathematical problem that had eluded humans for years. The researchers' role was to create an environment for the model to work in and then manually verify every claim, assuming full responsibility for the result.

Although this is theoretical work rather than an engineering product, the research could open a new path toward protocols that are impossible to break even in theory — not merely because of computational complexity, but because of the fundamental laws of physics. Deploying such schemes in key-exchange and authentication systems could completely reshape attacks on communication channels.