Study of Attacks on the HHL Quantum Algorithm

As the quantum research community continues to grow and new algorithms are designed, developed, and implemented, it is crucial to start thinking about security aspects and potential threats that could result in misuse of the algorithms, or jeopardize the information processed with these quantum algorithms. This work focuses on exploration of two types of potential attacks that could be deployed on a cloud-based quantum computer by an attacker circuit trying to interfere with victim circuit. The two attacks, called Improper Initialization Attack (IIA) and Higher Energy Attack (HEA), are for the first time applied to a well-known and widely used quantum algorithm: HHL. The HHL algorithm is used in the field of machine learning and big data for solving systems of linear equations. This work evaluates the effect of the attacks on different qubits within the HHL algorithm: ancilla qubit, clock qubit, and b qubit. This work demonstrates that the two attacks are able to cause incorrect results, even when only one of the qubits in the victim algorithm is attacked. Having discovered the vulnerabilities, the work motivates the need for future work to develop defense strategies for each of these attack scenarios.