Theodoros Trochatos

The cloud-based environments in which today's and future quantum computers will operate raise concerns about the security and privacy of user's intellectual property, whether code, or data, or both. Without dedicated security protections, quantum circuits submitted to cloud-based quantum computer providers could be accessed by the cloud provider, or malicious insiders working in the cloud provider's data centers. Furthermore, data embedded in these circuits can similarly be accessed as it is encoded using quantum gates inside the circuit. This study presents various hardware and architecture modifications that could be deployed in today's quantum computers, based on superconducting qubits, to protect both the code and data from potentially untrusted quantum computer providers or malicious insiders. Motivated by existing Trusted Execution Environments (TEEs) in classical computers, this study introduces the notion of Quantum Trusted Execution Environments (QTEEs) which leverage trusted hardware to hide or obfuscate quantum circuits executing on a remote, cloud-based quantum computer. This study presents multiple, different approaches to design of QTEEs and considers both hardware and architecture, as well as system software and operating system support necessary for realization of QTEEs. Overall, this study presents three hardware architectures, namely, QC-TEE, SoteriaQ, and CASQUE, that have been designed to protect users' circuits and data from potential threats originating from both malicious quantum computer cloud providers or insider attackers. This study further outlines a roadmap for other possible QTEEs that can be developed in the future, to account for different threat models or to support different types of quantum computer architectures.

With the growing reliance on cloud-based quantum computing, ensuring the confidentiality and integrity of quantum computations is paramount. Quantum Trusted Execution Environments (QTEEs) have been proposed to protect users' quantum circuits when they are submitted to remote cloud-based quantum computers. However, deployment of QTEEs necessitates a Quantum Operating Systems (QOS) that can support QTEEs hardware and operation. This work introduces the first architecture for a QOS to support and enable essential steps required for secure quantum task execution on cloud platforms.

The development of quantum computers has been advancing rapidly in recent years. As quantum computers become more widely accessible, potentially malicious users could try to execute their code on the machines to leak information from other users, to interfere with or manipulate the results of other users, or to reverse engineer the underlying quantum computer architecture and its intellectual property, for example. Among different security threats, previous work has demonstrated information leakage across the reset operations, and it then proposed a secure reset operation could be an enabling technology that allows the sharing of a quantum computer among different users, or among different quantum programs of the same user. This work first shows a set of new, extended reset operation attacks that could be more stealthy by hiding the intention of the attacker's circuit. This work shows various masking circuits and how attackers can retrieve information from the execution of a previous shot of a circuit, even if the masking circuit is used between the reset operation (of the victim, after the shot of the circuit is executed) and the measurement (of the attacker). Based on the uncovered new possible attacks, this work proposes a set of heuristic checks that could be applied at transpile time to check for the existence of malicious circuits that try to steal information via the attack on the reset operation. Unlike run-time protection or added secure reset gates, this work proposes a complimentary, compile-time security solution to the attacks on reset~operation.

Continued expansion of cloud computing offerings now includes SmartSSDs. A SmartSSD is a solid-state disk (SSD) augmented with an FPGA. Through public cloud providers, it is now possible to rent on-demand virtual machines enabled with SmartSSDs. Because of the FPGA component of the SmartSSD, cloud users who access the SmartSSD can instantiate custom circuits within the FPGA. This includes possibly malicious circuits for measurement of power and temperature. Normally, cloud users have no remote access to power and temperature data, but with SmartSSDs they could abuse the FPGA component to learn this information. This paper shows for the first time that heat generated by a cloud user accessing the SSD component of the SmartSSD and the resulting temperature increase, can be measured by a different cloud user accessing the FPGA component of the same SmartSSD by using the ring oscillators circuits to measure temperature. The thermal state remains elevated for a few minutes after the SSD is heated up and can be measured from the FPGA side by a subsequent user for up to a few minutes after the SSD heating is done. Further, in a future multi-tenant SmartSSD setting, the thermal changes can be measured in parallel if one user controls the SSD and the other the FPGA. Based on this temporal thermal state of the SmartSSD, a novel thermal communication channel is demonstrated for the first time.