Practical quantum digital signatures

Lead Research Organisation: Heriot-Watt University
Department Name: Sch of Engineering and Physical Science

Abstract

Digital signature schemes enable a message to be securely signed, so that one or more recipients can be sure of its authenticity. R. Rivest, one of the inventors of the widely used RSA algorithm for public key cryptography, wrote in 1990 that "The notion of a digital signature may prove to be one of the most fundamental and useful inventions of modern cryptography". Indeed, digital signature schemes are today used extensively e.g. in internet commerce, and are of immense economic importance. Unfortunately all known classical digital signature schemes rely on unproven computational assumptions for their security. Quantum digital signature schemes, on the other hand, can be made unconditionally secure based only on the validity of quantum mechanics, similar to how the security of quantum key distribution is guaranteed. Distribution of a secret cryptographic key ensures the privacy of an encrypted message. Authentication and digital signature schemes, on the other hand, ensure the integrity of a message. This is different but no less important. Key distribution for cryptography also requires some kind of separate authentication scheme in order to work, since otherwise one cannot know that one is talking to the right person (a so-called "man-in-the-middle attack" becomes possible).

Quantum key distribution is one of the very few applications of quantum technology that are already commercially available. In contrast to quantum key distribution, however, no experimentally feasible scheme for quantum digital signatures has been proposed, until now. Existing schemes for quantum digital signatures use non-orthogonal quantum states distributed as "quantum signatures". For a classical physical system, there is in principle no limit to how well we can determine its position, velocity, colour, and so on, only practical limitations depending on how good our measurement equipment is. In contrast, quantum states cannot even in principle be perfectly determined or distinguished from each other, no matter how technically perfect our equipment is. Only the distributing party has perfect knowledge of the quantum signatures, allowing only her to later sign messages by giving the full classical description of the states, which can then be tested against the signature states. The recipients must store the signature states in quantum memory until the distributing party wants to sign a message. This requirement for long-term quantum memory unfortunately makes existing protocols completely unfeasible in practice. Quantum states are very fragile and rapidly deteriorate, usually on a scale of milliseconds or faster.

I propose a setting where the recipients measure the quantum signature states immediately after distribution. The quantum measurement they should use sometimes identifies the state perfectly, but sometimes fails. Integrity of a signed message is now guaranteed since no adverse party (including other recipients) can provide the correct description of the signature states for all the cases where identification succeeded. Only the distributing party can do this. Transferrability of messages can be guaranteed if the recipients "compare" the signature states they receive. Comparing quantum states is not as straightforward as comparing classical systems, but is feasible. This project will address the important task of investigating the information-theoretic security of such digital signature schemes which crucially do not require quantum memory, and identify the best scheme(s) in terms of scaling of key length versus level of security, and experimental feasibility of measurements and other components required. In addition to this theoretical work, a proof-of-principle experimental implementation will then be made.

The ultimate technological, societal and economical impact of this work is potentially very large, due to the importance and wide use of digital signature schemes.

Planned Impact

Understanding how to manipulate quantum systems is of tremendous technological importance and may lead to huge economic payoffs. The investment in basic research by companies such as IBM, Lucent technologies (Bell Labs), Microsoft research, Hitachi, Fujitsu, and Toshiba is testament to the potential impact of quantum technologies. The proposed research contributes to this challenge. Quantum communication is an emerging technology which could provide security and authentication protocols for the digital economy. Quantum cryptography is already commercially available, and the proposed work paves the way for bringing quantum digital signatures to a similar level.

There is also a shortage of STEM skilled employees in the UK, and it appears that young people are being put off science before they enter higher education. Enthusing the public about STEM subjects is one way to counter this. It is also essential that the public knows about relevant research results in order to make informed decisions about important issues. Especially levels of female students are low in STEM subjects, and the 'leaky pipeline' is of great concern, i.e. the fact that a higher proportion of women than men abandon a career in STEM subjects even after obtaining an undergraduate or postgraduate degree, or further along. This represents a great loss to the UK economy. The proportion of female students continuing with a PhD in Physics is actually higher than for male students, which indicates that the issue most likely is not lack of motivation among female students and researchers. The proposed research has great potential to enthuse the general public, and the applicant and her team have a strong track record in outreach activities. The applicant has also led the Athena Swan effort for Physics at Heriot-Watt (www.athenaswan.org). The Athena Swan Charter is committed to the advancement of the careers of women in science, engineering and technology.
 
Description We have developed schemes for digital signatures, for which the security is guaranteed by the laws of quantum mechanics. We have theoretically investigated the security of such schemes, and built experimental prototypes to demonstrate viability in principle. The methods we have developed can in fact be implemented with the same experimental equipment as quantum key distribution, which is already commercially available, thus extending the usefulness of setups for quantum key distribution to provide also the functionality of digital signatures.
Digital signatures are widely used in electronic communications and commerce, and enable the sending of signed messages such that the messages cannot be tampered with, and so that the messages are transferrable. This is different from encryption of a message, but no less important.
All key findings are available open access. Some journal papers are gold open access, and for all papers, an equivalent version is available on www.arXiv.org and/or on the Heriot-Watt PURE web site.
Exploitation Route Further work is required e.g. on the security of quantum digital signatures, on finding the best quantum digital signature protocols, and how to best implement them.
We are taking first steps to commercialise our most efficient signature protocol (filed a patent Feb 2016, patent published 2017), in collaboration with Swedish company IT Secured.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Financial Services, and Management Consultancy,Healthcare,Government, Democracy and Justice,Security and Diplomacy

 
Description We have had interest from commercial providers of quantum key distribution (Toshiba Research, Cambridge and IdQuantique, Geneva) to implement our protocol. Toshiba research have implemented some of our protocols, but commercial application is however some time away still. There is also emerging interest from other researchers, mainly from the quantum cryptography research community and from computer scientists, to work on quantum digital signatures. Outside the scientific community there is however still, at this time, limited impact. Our work on quantum signatures is continuing as WP4 of the UK Quantum Technology Hub on Quantum Communication, and it is a little hard to say whether outcomes in the transition period between grants should be associated to one or the other grant, or both. In Feb 2016 we filed a patent for an efficient signature protocol, and the patent was published in 2017. Ryan Amiri, who started his PhD studies in September 2014, supervised by Erika Andersson, was awarded one of only 5 places in the Nature/Entrepreneur First Innovation Forum in Quantum Technologies, to work on an efficient signature protocol that can use quantum key distribution technology.
First Year Of Impact 2016
 
Description Blackett Review on Quantum Technologies
Geographic Reach National 
Policy Influence Type Gave evidence to a government review
URL https://www.gov.uk/government/publications/quantum-technologies-blackett-review
 
Description MSCA-ITN-2015-ETN - Marie Sklodowska-Curie Innovative Training Networks (ITN-ETN)
Amount € 3,924,884 (EUR)
Funding ID QCALL 675662 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 12/2016 
End 11/2020
 
Description UK Quantum Technology Hubs
Amount £24,093,966 (GBP)
Funding ID EP/M013472/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 12/2014 
End 11/2020
 
Description MPL, Erlangen 
Organisation Max Planck Society
Department Max Planck Institute for the Science of Light
Country Germany 
Sector Public 
PI Contribution Collaboration on extending and realising quantum signature protocols. Experimental realisation of a protocol using homodyne measurements has been carried out at MPL, with theoretical support from the groups at Heriot-Watt and St Andrews.
Collaborator Contribution Collaboration on extending and realising quantum signature protocols. Experimental realisation of a protocol using homodyne measurements has been carried out at MPL, with theoretical support from the groups at Heriot-Watt and St Andrews.
Impact Results are reported in Croal et al., Physical Review Letters 117, 100503 (2016).
Start Year 2015
 
Description NICT 
Organisation NICT National Institute of Information and Communications Technology
Country Japan 
Sector Public 
PI Contribution NICT and Heriot-Watt both have long-standing research interests in quantum communication technology. Although this collaboration started before EP/K022717/1 ended, it is associated with this grant, as it arose through our work in this grant. We are continuing our work on quantum signatures, within this collaboration in the form of several research visits and a staff exchange in January 2016 (R Collins and R Amiri, both from Heriot-Watt, visited NICT to work on quantum signatures). On 14-19 March 2016, Gerald Buller and Erika Andersson visited Tokyo, funded by the Government Department for Business, Innovation and Skills (BIS) for a Quantum Technology Workshop and to discuss a possible research agreement between UK and Japan, on Quantum Communication.
Collaborator Contribution NICT have acted as hosts, providing accommodation for UK visiting researchers at no cost to the UK team members.
Impact A formal MoU on research collaboration has been put in place between NICT and Heriot-Watt.
Start Year 2015
 
Description QCALL partnership 
Organisation Heinrich Heine University Düsseldorf
Country Germany 
Sector Academic/University 
PI Contribution Based on our work on quantum signatures, we were invited to be an associated partner in the EU project QCALL (EU project 675662), which is an ITN (Innovative Training Network) funded by the Marie Sklodowska Curie Call H2020-MSCA-ITN-2015. This project runs 1 Dec 2016-30 Nov 2020.
Collaborator Contribution We have agreed to host visits by PhD students funded by the ITN.
Impact None yet (grant started Dec 2016).
Start Year 2016
 
Description QCALL partnership 
Organisation ID Quantique
Country Switzerland 
Sector Private 
PI Contribution Based on our work on quantum signatures, we were invited to be an associated partner in the EU project QCALL (EU project 675662), which is an ITN (Innovative Training Network) funded by the Marie Sklodowska Curie Call H2020-MSCA-ITN-2015. This project runs 1 Dec 2016-30 Nov 2020.
Collaborator Contribution We have agreed to host visits by PhD students funded by the ITN.
Impact None yet (grant started Dec 2016).
Start Year 2016
 
Description QCALL partnership 
Organisation National Center for Scientific Research (Centre National de la Recherche Scientifique CNRS)
Country France 
Sector Public 
PI Contribution Based on our work on quantum signatures, we were invited to be an associated partner in the EU project QCALL (EU project 675662), which is an ITN (Innovative Training Network) funded by the Marie Sklodowska Curie Call H2020-MSCA-ITN-2015. This project runs 1 Dec 2016-30 Nov 2020.
Collaborator Contribution We have agreed to host visits by PhD students funded by the ITN.
Impact None yet (grant started Dec 2016).
Start Year 2016
 
Description QCALL partnership 
Organisation Toshiba Research Europe Ltd
Country United Kingdom 
Sector Private 
PI Contribution Based on our work on quantum signatures, we were invited to be an associated partner in the EU project QCALL (EU project 675662), which is an ITN (Innovative Training Network) funded by the Marie Sklodowska Curie Call H2020-MSCA-ITN-2015. This project runs 1 Dec 2016-30 Nov 2020.
Collaborator Contribution We have agreed to host visits by PhD students funded by the ITN.
Impact None yet (grant started Dec 2016).
Start Year 2016
 
Description QCALL partnership 
Organisation University of Geneva
Department Department of Physics
Country Switzerland 
Sector Academic/University 
PI Contribution Based on our work on quantum signatures, we were invited to be an associated partner in the EU project QCALL (EU project 675662), which is an ITN (Innovative Training Network) funded by the Marie Sklodowska Curie Call H2020-MSCA-ITN-2015. This project runs 1 Dec 2016-30 Nov 2020.
Collaborator Contribution We have agreed to host visits by PhD students funded by the ITN.
Impact None yet (grant started Dec 2016).
Start Year 2016
 
Description QCALL partnership 
Organisation University of Leeds
Department School of Electronic and Electrical Engineering Leeds
Country United Kingdom 
Sector Academic/University 
PI Contribution Based on our work on quantum signatures, we were invited to be an associated partner in the EU project QCALL (EU project 675662), which is an ITN (Innovative Training Network) funded by the Marie Sklodowska Curie Call H2020-MSCA-ITN-2015. This project runs 1 Dec 2016-30 Nov 2020.
Collaborator Contribution We have agreed to host visits by PhD students funded by the ITN.
Impact None yet (grant started Dec 2016).
Start Year 2016
 
Description QCALL partnership 
Organisation University of Padova
Department Department of Information Engineering
Country Italy 
Sector Academic/University 
PI Contribution Based on our work on quantum signatures, we were invited to be an associated partner in the EU project QCALL (EU project 675662), which is an ITN (Innovative Training Network) funded by the Marie Sklodowska Curie Call H2020-MSCA-ITN-2015. This project runs 1 Dec 2016-30 Nov 2020.
Collaborator Contribution We have agreed to host visits by PhD students funded by the ITN.
Impact None yet (grant started Dec 2016).
Start Year 2016
 
Description QCALL partnership 
Organisation University of Vigo
Department School of Telecommunications Engineering
PI Contribution Based on our work on quantum signatures, we were invited to be an associated partner in the EU project QCALL (EU project 675662), which is an ITN (Innovative Training Network) funded by the Marie Sklodowska Curie Call H2020-MSCA-ITN-2015. This project runs 1 Dec 2016-30 Nov 2020.
Collaborator Contribution We have agreed to host visits by PhD students funded by the ITN.
Impact None yet (grant started Dec 2016).
Start Year 2016
 
Description St Andrews University 
Organisation University of St Andrews
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaboration on quantum signatures, realising and extending previous work.
Collaborator Contribution Collaboration on quantum signatures, realising and extending previous work. Realisation at Max Planck Institute of Light, Erlangen, Germany.
Impact Results are reported in Croal et al., Physical Review Letter 117, 100503 (2016).
Start Year 2015
 
Description Toshiba Research 
Organisation Toshiba Research Europe Ltd
Department Cambridge Research Laboratory - Toshiba
Country United Kingdom 
Sector Private 
PI Contribution Based on the work in EP/K022717/1, Dr Erika Andersson, Dr Robert Collins and Prof Gerald Buller visited Toshiba Research in Cambridge on 17 October 2014. Toshiba Research, are developing equipment for quantum key distribution. We have continued to develop quantum communication protocols to be implemented by Toshiba Research (currently as part of the UK Quantum Technology Hub on Quantum Communication).
Collaborator Contribution Toshiba Research, who are developing equipment for quantum key distribution, will implement the procedures for quantum digital signatures we have developed using their experimental setups.
Impact Visit to Toshiba Cambridge as mentioned above, and informal agreement to collaborate. A paper on an implementation by Toshiba of a scheme for measurement-device-independent signatures developed by our team has recently been submitted. This is funded by further collaboration through the UK Quantum Technology Hub on Quantum Communication.
Start Year 2014
 
Description University of Cambridge 
Organisation University of Cambridge
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaborative research on novel protocols for quantum digital signatures, with Adrian Kent from University of Cambridge. In particular, we have jointly proved that certain protocols are secure against general forging attacks, where recipients can use quantum entanglement.
Collaborator Contribution Collaborative research on novel protocols for quantum digital signatures, with Adrian Kent from University of Cambridge. In particular, we have jointly proved that certain protocols are secure against general forging attacks, where recipients can use quantum entanglement.
Impact Joint publications wit A Kent as reported under publications.
Start Year 2014
 
Description University of Waterloo 
Organisation University of Waterloo
Country Canada 
Sector Academic/University 
PI Contribution Staff time; Dr Erika Andersson and Dr Petros Wallden visited University of Waterloo in August 2014 to initiate a collaboration with the group of Prof Norbert Luetkenhaus.
Collaborator Contribution Staff time for Prof Norbert Luetkenhaus and Mr Juan Miguel Arrazola (PhD student at IQC, Waterloo).
Impact Dr Erika Andersson and Dr Petros Wallden visited University of Waterloo in August 2014 to initiate collaboration with the group of Prof Norbert Luetkenhaus. Joint publications with Juan Miguel Arrazola, who obtained his PhD with Prof Luetkenhaus as supervisor, are reported in the publications section.
Start Year 2014
 
Title Method and system for assurance of message integrity 
Description This is a method for transferrable message authentication, inspired by our work on quantum signatures. The present disclosure relates to a computer-implemented method for assurance of message integrity for a message transmitted within a network environment. The disclosure also relates to a corresponding communication system and to a computer program product. 
IP Reference WO2017135866A1 
Protection Patent application published
Year Protection Granted 2017
Licensed No
Impact A Swedish company, IT Secured, with whom one of the inventors is affiliated, is involved in developing the invention.
 
Description Kosmos article 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact I wrote an article on quantum computers, "Quantum computers - supercomputers in superposition", for the yearbook of the Swedish Physical Society. The level of the article, written in Swedish, is suitable for anybody with school-level physics.
Year(s) Of Engagement Activity 2017
URL http://www.fysikersamfundet.se/kosmos/
 
Description New Scientist Instant Experts event on the quantum world 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact I gave a well-received introductory talk at a New Scientist "Instant Experts" event in London on 14 October 2017
Year(s) Of Engagement Activity 2017
URL https://www.facebook.com/events/729470520568475/