Advanced Cryptography for the Quantum Age

Digital technologies play a central role in our daily lives, from communication and banking to healthcare and cloud services. Cryptography is the science that protects the security and integrity of such systems, by protecting sensitive information, validating identities, and ensuring that data can be used safely.

The emergence of quantum computers poses new risks for cryptography, as existing schemes may not be secure against a quantum adversary. It also offers new opportunities in the form of new cryptographic capabilities that the new technology would enable.

Project ACQUA prepares tools and techiniques for cryptography in a quantum age. Our focus is not on near term solutions, but rather on the possibility of achieving the most elaborate cryptographic functionality using quantum resources. A particular emphasis of our project is on cryptographic solutions for remote creation, processing and utilization of classical and quantum data.

To this end we study the foundations of computational hardness in the quantum setting, we study the possibilities of achieving strong cryptography that is usable by non-quantum users but is secure even against quantum attackers, and study the ability for securely manipulating quantum data, both locally and remotely.

Project ACQUA aims to ensure that even in a strongly-quantum future, digital systems remain secure and trustworthy. This is important for many applications, including cloud computing, secure communication, and emerging quantum technologies.

Project ACQUA has invested significant research resources in all of the project goals and made important advances towards achieving its goals of providing a secure quantum future. The project team has already published a number of papers in the world’s leading venue in the area of cryptography and theoretical computer science, and is continuing to push the envelope in studying what is achievable cryptographically using quantum resources.

One aspect that has been extensively studied is the foundations of quantum hardness. Namely the very basic mathematical structures that allow for cryptography to exist in the quantum era. A particular emphasis was put on the study of the notion of pseudorandomness. Pseudorandom objects mimic the behavior of random ones while having much simpler structure. Our project investigates this notion in various angles, including the existence and utility of pseudorandom quantum states, the existence of pseudorandom quantum operators, and the ability to create an analogous notion of “pseudo-entanglement” that mimics entanglement (the quantum correlations that underly many of the unique phenomenons of quantum information theory).

Another aspect that is being researched is the ability to construct post-quantum secure systems. These are systems that can be used by standard, non-quantum, users, but such that even quantum attackers cannot break their security. Such constructions are known for many “simple” cryptographic applications, but some very important ones still remain outside reach. This includes, for example, the notion of program obfuscation: a way to make computer programs hard to reverse-engineer, without damanging their functionality. Program obfuscation with quantum security is a central research goal. Additionally we consider the ability to produce short proofs of (classical) computation such that even a quantum attacker cannot produce a proof of a false statement.

A third focal point is the ability to produce highly-functional cryptography in a fully quantum era (far beyond what is provided by current quantum computers, but within the limit that is theoretically achievable with proper technology). In this context one can consider program obfuscation of quantum programs, a subject on which we made notable progress. We may also consider settings where a classical client wishes to utilize a remote untrusted quantum server.

Overall, the project has both deepened the understanding of security in the quantum world and created new tools that can be used in future technologies.

The results of ACQUA go beyond current knowledge in several important ways. They enhance our understanding of the mathematical foundations of cryptography that is based on quantum information, and what may and may not be possible under certain mathematical structures. They also show that quantum computers can in principle offer advanced cryptoraphic functionality such as securely and verifiably computing on remote data.

Whereas some of our results are meant to run on standard computers and only withstand quantum attacks, others results utilize quantum computing to perform computational tasks. For the latter, one requires a so-called “scalable” quantum computer. One that can perform arbitrary computations that are guaranteed by quantum theory. These capabilities are far beyond the currently existing quantum computers, but there are strong theoretical evidence that building them is a matter of (challenging yet surmountable) engineering effort.

Further research will be needed to make our methods more efficient, and to create the hardware that will be able to support it, so that it is ready for practical use. Our vision is that in the future, these advances could support secure quantum cloud services, stronger protection of digital information, and new ways to ensure trust in digital systems.

By combining new ideas with practical tools, ACQUA helps prepare society for a future where quantum technologies are part of everyday life.

Periodic Reporting for period 1 - ACQUA (Advanced Cryptography for the Quantum Age)

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