CLOAQ: Combined Logic and Angle Obfuscation for Quantum Circuits

TL;DR

CLOAQ introduces a novel quantum circuit obfuscation method that combines logic and angle obfuscation to better protect quantum circuit designs from theft and tampering, demonstrating increased resilience against attacks.

Contribution

This work presents CLOAQ, the first approach to combine logic and phase obfuscation in quantum circuits, enhancing security against untrusted quantum compilers.

Findings

CLOAQ effectively hides circuit logic and phase angles.

Combined obfuscation increases resilience to attacks.

Sampling from the full Hilbert space improves evaluation accuracy.

Abstract

In the realm of quantum computing, quantum circuits serve as essential depictions of quantum algorithms, which are then compiled into executable operations for quantum computations. Quantum compilers are responsible for converting these algorithmic quantum circuits into versions compatible with specific quantum hardware, thus connecting quantum software with hardware. Nevertheless, untrusted quantum compilers present notable threats. They have the potential to result in the theft of quantum circuit designs and jeopardize sensitive intellectual property (IP). In this work, we propose CLOAQ, a quantum circuit obfuscation (QCO) approach that hides the logic and the phase angles of selected gates within the obfuscated quantum circuit. To evaluate the effectiveness of CLOAQ, we sample the input state uniformly from the Hilbert space of all qubits, which is more accurate than prior work that use all-|0> inputs. Our results show that CLOAQ benefits from the synergy between logic and phase protections. Compared with prior QCO approaches using only one perspective, the combined method is more resilient to attacks and causes greater functional disruption when the unlocking key is incorrect.