Quantum Program Obfuscation Technique 'Clock' Enhances Security for Cloud-Based Quantum Computing

Researchers Vivek and Amel from the Singapore Institute of Technology presented Clock, a quantum program obfuscation technique designed to protect sensitive outputs when executing quantum algorithms on untrusted cloud-based quantum computers. The method addresses three attack surfaces in quantum cloud computing: input data, the algorithm itself, and output results, with Clock specifically targeting the latter by adding random quantum gates before measurement to corrupt results, then classically reversing the obfuscation locally without requiring a quantum computer. Prior obfuscation schemes either added unnecessary qubits, blocked optimization, or required local quantum hardware, whereas Clock avoids these limitations by working within existing resources, preserving optimization, and supporting a wide range of circuits. The technique was demonstrated at Black Hat Asia 2025, building on their 2024 work that introduced ObfuscateQ, a framework with nine algorithms for circuit-level and code-level obfuscation. Clock’s effectiveness was measured using Total Variation Distance (TVD), achieving a score of 0.8—significantly higher than prior methods (0.4–0.7)—indicating superior output corruption. The researchers provided a web interface, white paper, and Docker implementation for independent verification, emphasizing the growing importance of quantum-classical hybrid security as quantum computing adoption accelerates.