Researchers at IonQ Inc. and NTT Research have demonstrated a separation between quantum public key encryption (qPKE) and quantum one-way functions (qOWFs), revealing that qPKE is possible even without qOWFs under specific conditions involving what’s known as an oracle, a theoretical computing component with defined properties. Building secure quantum public key encryption, a method for encrypting information using principles of quantum mechanics with classically readable messages, doesn’t necessarily depend on “quantum one-way functions”.

These functions are considered a strong requirement in traditional cryptography, but this work reveals an alternative path; qPKE is possible without them under specific conditions involving theoretical computing components called oracles. Researchers at IonQ Inc. and NTT Research have demonstrated a surprising result in quantum cryptography: secure public-key encryption doesn’t necessarily rely on “quantum one-way functions”. These functions, imagine a lock so complex that even a quantum computer cannot pick it, yet proving its existence is difficult, have long been considered essential building blocks.

The team showed qPKE (quantum public key encryption) can exist without these traditionally required elements, challenging established assumptions about the foundations of secure communication. This finding builds upon previous research showing similar relaxations for other cryptographic primitives like digital signatures, but leaves open the question of exactly what does underpin truly robust quantum public-key systems with classical keys and communications.

Quantum Encryption Achieves Independence From One Way Functions

IonQ Inc. Achieving secure communication without relying on traditionally key “one-way” computational problems marks progress over prior work, which showed similar relaxations for digital signatures but left open questions about strong systems. Under certain conditions involving unitary, real, and self-inverse oracles, theoretical computing components, a functioning qPKE scheme can exist even when qOWFs do not; this finding clarifies the possibilities within quantum cryptography. These oracles also allow for point-function obfuscation, masking function logic and ruling out simple constructions of quantum one-way functions from such obfuscations.

Fortunately, researchers constructed qPKE utilising quantum indistinguishability obfuscation alongside efficiently verifiable one-way puzzles, a potentially weaker assumption than relying on qOWFs. This construction mirrors classical methods used to build public key encryption but adapts them for quantum computation with classical communication. Practical implementations suitable for widespread use remain elusive however, as significant engineering challenges persist in building stable and scalable quantum systems required to realise these theoretical schemes.

Post-Quantum Encryption Relies On New Cryptographic Assumptions

IonQ Inc. The team’s construction hinges upon assumptions about quantum indistinguishability obfuscation, essentially scrambling code so thoroughly that its purpose remains hidden, and efficiently verifiable puzzles, cryptographic tools with unresolved long-term security questions in a post-quantum world. This work broadens our understanding of what is achievable in post-quantum cryptography by demonstrating that public key encryption does not require quantum one-way functions.

A definitive demonstration was achieved using theoretical computing components called oracles possessing specific properties: unitary, real, and self-inverse. This separation demonstrates an alternative pathway to building strong quantum communication systems based instead upon potentially weaker foundations like quantum indistinguishability obfuscation alongside efficiently verifiable puzzles.

Researchers demonstrated that public-key encryption with classical keys and ciphertexts does not necessitate the existence of quantum one-way functions. Using specifically defined theoretical tools known as oracles, which are unitary, real, and self-inverse, they showed it is possible to construct this type of encryption without relying on these traditionally assumed components. This work clarifies relationships between various post-quantum primitives and expands options for building such systems.

👉 More information
🗞 Quantum Cryptomania with Classical Communication without One-Way Functions
✍️ Mohammed Barhoush and Amit Behera (IonQ Inc)
🧠 ArXiv: https://arxiv.org/abs/2610.32145

More like this