Quantum Technology: A next generation solution for secure communication

Transcription

1 Quantum Technology: A next generation solution for secure communication Abdul R Mirza 1,2 and Francesco Petruccione 1,2,3 1 University of KwaZulu-Natal, Westville Campus, Durban, South Africa 2 QZN Technology (Pty) Ltd, Durban South Africa 3National Institute for Theoretical Physics, South Africa Abstract: Quantum Information Processing and Communication has the capability to revolutionize the ICT sector in the 21st Century, as did the semiconductor-based transistor in the previous century (USA United States of America, Committee on Technology, National Science and Technology Council, 2008). It fuses the laws of quantum physics into the current ICT framework to expand the limits of conventional ICT solutions. Quantum communication is the most advanced QIPC technology. It is driven by quantum encryption or, more correctly, Quantum Key Distribution (QKD): a secure method of transferring encryption keys between two distant parties, thus forming the base for inviolable global communication networks (Austria, ERA PROJECT Quantum Information Sciences and Technologies, 2005). This method of encryption differs from conventional methods in that it encodes data within quantum two-level systems (qubits). One is therefore required to physically measure the qubit in order to retrieve any intelligible data. As the measurement of an observable in a quantum system creates a perturbation in the complementary properties of the system, an eavesdropper will necessarily need to break the established laws of quantum mechanics in order to decipher the data while remaining unnoticed. Many physicists have mathematically proven that QKD is completely secure even if an insecure communication channel is used. This security is further independent of the adversary s technological advantage. Charles Bennett and Gilles Brassard initially developed the technology in 1984 as the BB84 protocol (Bennet and Brassard. 1984). Since then, a global effort has been undertaken in order to bring QKD on par with current ICT technology and mature the technology to an industrially acceptable standard. In this paper we provide an overview of this technology and its current status. Introduction: Conventional Information and Communication Technology (ICT) services the ever-growing need of today s knowledge-based society. Consumers continuously demand for faster, smaller and ecofriendly devices. This has necessitated the higher packaging density of components on computer chips to decrease inter-communication times. With this trend set to continue, the electrons per device will continue to decrease exponentially and are predicted to enter the quantum regime by 2015 (Spiller 2006). In accordance to Moore s Law, this has driven the ICT sector into the quantum paradigm by operating at an atomic scale where coherent quantum mechanical processes begin to dominate the physical properties. Quantum mechanical principles will therefore no longer be negligible in conventional data manipulation techniques. This has created a need for an alternative approach to information technology to provide capabilities beyond what conventional concepts can offer. Quantum Information Processing and Communication (QIPC) limits the technological manipulation of information only by the laws of physics (Corker 2005). Information can therefore be characterized, quantified and processed using the basic rules of quantum mechanics. Exploiting some of the fundamental features of the quantum world, such as Heisenberg s uncertainty principle, superposition and entanglement (Nielsen, 2000), QIPC is an enabling resource for future ICT solutions. Quantum cryptography is the most matured field in QIPC. The process uses a physical encoding of a quantum data carrier to secure communications at an OSI layer 1 level. It has been catalysed by the continuously expanding e-commerce industry, developments in efficient quantum factorization and the fact that quantum cryptography is the only known solution to provide long term data security (Corker 2005). The cryptographic industry has realized the potential threat that quantum computing and mathematical developments pose to conventional cryptography and therefore many leading IT firms (Toshiba, NECTEC, IBM, HP) have invested into the development of quantum

2 cryptographic technology while other companies dedicated to quantum-based technologies (QZN Technology) have been established in the past few years to cater for this emerging market. Various other quantum-powered technologies exist today. A quantum Random Number Generator (RNG) produces random bits as the result of a hardware-based, quantum physical process. This method of generation is therefore independent of the user environment unlike software-based generators commonly in use today. A generator with any form of dependence may be predictable to a certain degree and therefore create a compromise in the security system. Single photon sources and detectors are further quantum-enabled technologies with an extremely high intensity resolution. The devices are designed to produce and detect quantum particles of light (photons). This provides the basis for high precision instrumentation for application in research, sensory, imaging and metrology markets. Conventional Encryption Conventional key distribution routines, such as the Deffie-Hellman method [2], use mathematical algorithms to encapsulate the key bits during its distribution process. In particular, they use oneway functions that can efficiently be computed in one direction but require large resources to compute the inverse function. This makes the decryption infeasible relative to the value of the encrypted data. In the case of public key cryptography, the multiplication of large prime numbers serves as the one-way function. Due to the mathematical nature of the scheme, it is susceptible to decryption through advances in computing power and potential mathematical discoveries. This potentially compromises the future integrity and security of information encrypted in such a manner. Conventional techniques of parallel computing continue to challenge today s communication security standards within reasonable time scales. A prime example of this is the decipherment of the RSA 1024 encryption algorithm in 100 hours by researchers at the University of Michigan in May 2010 (Pellegrini 2010). Further to this, the nature of quantum computers provides an intrinsic capability to efficiently decipher current cryptographic systems (Nielsen 2000). Thus the development of such computing power will render conventional cryptography obsolete. Quantum-powered Encryption Quantum communication, or more correctly named, Quantum Key Distribution (QKD), is a cryptographic primitive for the generation of secure random cryptographic keys. It encodes the key bits using a physical parameter of a quantum two-level system (qubit). In this case, the qubit is the data carrier and hence any form of data retrieval requires a measurement of a physical property of the qubit. As the qubit evolves within a quantum regime, it obeys the respective laws. As the properties of quantum mechanical particles change fluidly when an observer interacts with them, there is no way to determine its complete quantum nature. The measurements of certain parameters of a quantum system create perturbations in the various other characteristics of system. This is known as Heisenberg s Uncertainty Principle and provides an intrinsic physical security for the next generation of communication systems. QKD shifts the security basis away from algorithms towards physical techniques of security through the encapsulation of data in quantum mechanical particles. Any form of measurement by an unauthorized party will result in a change of the qubit. The users will necessarily detect this, thus exposing any eavesdropper. QKD therefore offers secure communication independently of an adversary s technological advantage (Renner 2005).

3 Figure 1: The BB84 protocol is based on the fact that the two polarization sets are indistinguishable if encoded onto a single particle of light. This ensures that if an eavesdropper tries to intercept the communication, she will create errors, thereby notifying the legitimate users. Though there are many different ways to implement QKD, the original procedure that is still use by many platforms today encodes information within the polarization of light. Light is an electromagnetic wave that vibrates in a particular orientation. This phenomenon is known as polarization. A Polaroid sheet is only transparent to light of a particular polarization. This reduces the intensity of the light and may also shift the orientation of the polarization if the light and Polaroid are incorrectly aligned. In quantum cryptography the above principle is adapted for use with single particles of light - photons. The sender, Alice, transmits polarized photons to Bob, the receiver. Alice is able to choose the polarization in one of four options: horizontal, vertical, diagonal, or antidiagonal. The former (horizontal and vertical) and latter (diagonal and antidiagonal) pairs form two bases of transmission as shown in Figure 1. Due to the quantum superposition principle [], Eve, the eavesdropper, cannot distinguish the state of the sent particles with absolute certainty. When Bob receives a photon he randomly measures it on one of the bases. Due to Bob s measurement strategy, he will measure the photons in the correct basis 50% of the time. If Bob chooses the same basis as Alice, he will of course achieve the correct result. In any other case his results will be wrong or right with equal probability due to the superposition principle. This is illustrated in Table 1. Once the transmission of the photons is complete, Alice and Bob compare only the bases used in preparing and measuring the photons. This process, together with error correction and privacy amplification techniques, ensures that all the remaining bits in the key are identical, therefore providing a symmetric key for use in encryption. An unnoticed interception of photons by Eve is not possible since any measurement will destroy, or at the least alter, the polarization of the photon. By verifying the correctness of the final key, the users are able to predict if Eve was indeed eavesdropping. Table 1: If Alice and Bob transmit and measure on a common basis, a deterministic result should be obtained. However, the photon has a 50% probability to be measured in either state if Alice and Bob use different bases. In such a case the photons are discarded, thereby both parties have identical key streams after the completion of post-distribution processes. Alice s States Bob s Measurement Basis 100% 100% 50% 50% 50% 50% 100% 100% Quantum networks In the last decade the industry has witnessed great advances in photonic QKD technology with the research, development and commercialization of automated QKD devices by both academia and the corporate sector. However, these early generation solutions have appealed only to a niche

4 market due to QKD technology's bottleneck effect on the current ICT infrastructure. This is due to the stringent requirements of the qubit. The intrinsic absorption within the communication channel, together with the current lack to regeneration abilities for an optical qubit, has limited the key distribution distance of a photon to a distance of 120 km (Zhen-Qiang 2008) before it is absorbed. Thus one of the major bottlenecks in the commercialization of QKD is the limited spatial coverage that QKD offers. The recent investigations into quantum networking techniques have served to address this issue. Recent efforts have been made in developing QKD networks such as the Durban-QuantumCity project (Mirza 2010), SECOQC (Peev 2009), SwissQuantum (idq 2011) and Tokyo QKD network (Sasaki 2011). The QuantumCity initiative was launched in 2009 and is still currently operational. It is a star-topology network comprising of four nodes and running along the ethekwini municipality s optical infrastructure. The European FP6 project Secure Communication using Quantum Cryptography (SECOQC) project aimed to standardize QKD technology through a cross-platform interface allowing the integration of various QKD systems into one network known as the Quantum Back Bone network. The Durban-QuantumCity project seeks to test the long-term performance of QKD devices in a commercial environment. The City of Durban possesses optical fibre infrastructure that is primarily used to link the vital services of the Municipality [9]. The network is also available to educational institutes, hospitals and other corporates with the vision of providing broadband access to all residents in the City of Durban. The QuantumCity project uses this fibre infrastructure to provide QKD-secured communication between nodes on the network. This is the first time QKD systems have been deployed as a network in a commercial environment for extended periods of time. The QuantumStadium project was an extension of the QuantumCity project. It encrypted the link between Durban's Moses Mabhida Stadium in Durban and the ethekwini s offsite Joint Operations Centre. The system uses a layer 2 encryption process with an AES encryption scheme, but features a quantum-based key distribution system. The quantum communication link secures telephone, internet, video, data and traffic travelling across the fibre optic link at up to 1 Gigabit per second. Global QKD network Such link lengths are typical of a Municipal Area Network (MAN) and the examples have been mentioned above. A QKD solution spanning a global network will however require further investigation. The use of satellite technology in achieving a global quantum secured communication network has been of interest in the past few years. Many feasibility tests have been conducted (Bonato 2009 and Toyoshima 2011) however various challenges still prevent the realization of a ground to satellite QKD link. In this technique the satellites are considered to be trusted nodes. The nodes travel between various MANs creating a global backbone encryption key resource. The satellite network therefore requires an access point at each participating MAN network. The access point will require, further to a robust QKD link, the communication infrastructure to provide gateway functionality to the Metropolitan area. Unfortunately, most feasible sites for ground-to-satellite QKD links are in relatively remote and isolated in their surroundings. Although this ensures better visibility, it lacks the infrastructure to support a commercial global access point. As parallel step to the development of satellite-based global QKD networks, we are investigating the use of the commercial aircrafts network as secure transport mechanism to support the global QKD network. Commercial airliners create an ideal alternate global network for key distribution in terms of coverage, reliability and contact time. Further the airports at each connected city have the appropriate supporting infrastructure to serve as an access point for the MANs to the global network. The QKD process, implemented in the proposed scheme, will occur whilst the aircraft is docked at the airport. This allows a simple fibre-based QKD system is to be used for the key distribution

5 process. Due to the use of a fibre channel, the solution bypasses the additional synchronization techniques required when using a satellite-based network. The frequency and reliability of the link, further enhances the opportunities of this option. The initial systems that are to be used will require the aircraft to be a trusted zone although certified tamper-proofing techniques will be used. The long-term objective is to upgrade these initial systems to contain a quantum memory and an entangled photon source for QKD. As with the satellite solution, this would provide the idea untrusted network scenario. The commercial airliners are to serve as a global link between the MANs of connected cities, as such the airports serve as gateways. Each aircraft will be fitted with a tamper-proof QKD unit in the communications hub in the hull of the aircraft. This is a highly restricted zone and can therefore be assumed a secure location. This unit will be responsible for the quantum-secured key distribution between itself and the sister unit stationed in the respective airport. The secure key management layer, from within the airport building, will then manage the keys. This, in total will provide the access point to the MAN. Information can be encrypted on site and safely propagated through conventional communication networks or the keys sold onwards to the respective clients. Conclusion: It has only during the last 30 years that many of the theoretical and almost unintuitive predictions of quantum mechanics could be realised in the laboratory. Presently, we are witnessing the second quantum revolution, the quantum technology revolution. The miniaturization of technological devices necessitates the manipulation of objects at the nanoscale level, where coherent quantum mechanical processes start to dominate the physical properties. Among the basic tools of the new quantum technologies are quantum information, quantum computation, quantum metrology, quantum communication, and quantum control. Quantum cryptography has been the leading technology in this race. Today it is available as a commercial product to niche markets. Active research is however presently being conducted to further enhance the quality of service of this product to match the needs of the current information based society we live in today. References: Austria, ERA PROJECT Quantum Information Sciences and Technologies. (2005). Quantum Information Processing and Communication. Strategic Report on Current Status, Visions, and Goals for Research in Europe, Innsbruck. Bennett C.H. and Brassard G. (1984). Quantum Cryptography: Public key distribution and coin tossing. Proceedings of the IEEE International Conference on Computers, Systems, and Signal Processing. Bangalore. Bonato C, Tomaello A, Da Deppo V, Naletto G and Villoresi P (2009) Feasibility Analysis for Quantum Key Distribution between a LEO Satellite and Earth. New J. Phys Corker D., Ellsmore P., Abdullah F. and Howlett I. (2005). Commercial Prospects for Quantum Information Processing. Thesis submitted to fulfil the requirements of the MBA degree. The Saïd Business School, University of Oxford. idq (2010) SwissQuantum [online]. Available from: Nielsen M.A. and Chuang I.L. (2000) Quantum Computation and Quantum Information. Cambridge: Cambridge University Press. Peev M et.al. (2009) The SECOQC quantum key distribution network in Vienna. New J. of Phys Pellegrini A., Bertacco V. and Austin T. (2010) Fault-Based Attack of RSA Authentication. Proceedings of the Conference on Design, Automation and Test in Europe. Leuven, Belgium. Renner R., Gisin N. and Kraus B. (2005) Information-theoretic security proof for quantumkey-distribution protocols. Phys Rev A

6 Sasaki M et.al. (2011) Field test of quantum key distribution in the Tokyo QKD Network. Optics Express Spiller T.P. and Munro W. J. (2006) Towards a Quantum Information Technology Industry. J. Phys.: Condens. Matter 18, V1 V10. Toyoshima M, Takenaka H, Shoji Y, Takayama Y, Takeoka M, Fujiwara M and Sasaki M (2011) Polarization-Basis Tracking Scheme in Satellite Quantum Key Distribution. Intl J. of Optics United States of America, Committee on Technology, National Science and Technology Council. (2008). A federal Vision for Quantum information Science, Washington. Zhen-Qiang Y., Zheng-Fu H., Wei C., Fang-Xing X., Qing-Lin W. and Guang-Can G. (2008) Experimental Decoy State Quantum Key Distribution Over 120km Fibre. Chinese Phys. Lett