Quantum cryptography: Difference between revisions

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{{Use dmy dates|date=September 2020}}

'''Quantum cryptography''' is the science of exploiting [[Quantum mechanics|quantum mechanical]] properties such as quantum entanglement, measurement disturbance, no-cloning theorem, and the principle of superposition to perform various [[cryptographic]] tasks.<ref>{{Cite journal|last1=Gisin|first1=Nicolas|last2=Ribordy|first2=Grégoire|last3=Tittel|first3=Wolfgang|last4=Zbinden|first4=Hugo|display-authors=|year=2002|title=Quantum cryptography|url=https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.74.145|journal=Reviews of Modern Physics|volume=74|issue=1|pages=145–195|doi=10.1103/RevModPhys.74.145|arxiv=quant-ph/0101098|bibcode=2002RvMP...74..145G|s2cid=6979295}}</ref><ref name=":4">{{Cite journal|last1=Pirandola|first1=S.|last2=Andersen|first2=U. L.|last3=Banchi|first3=L.|last4=Berta|first4=M.|last5=Bunandar|first5=D.|last6=Colbeck|first6=R.|last7=Englund|first7=D.|last8=Gehring|first8=T.|last9=Lupo|first9=C.|last10=Ottaviani|first10=C.|last11=Pereira|first11=J. L.|display-authors=et al.|year=2020|title=Advances in quantum cryptography|url=https://www.osapublishing.org/aop/abstract.cfm?uri=aop-12-4-1012|journal=Advances in Optics and Photonics|volume=12|issue=4|pages=1012–1236|arxiv=1906.01645|doi=10.1364/AOP.361502|bibcode=2020AdOP...12.1012P|s2cid=174799187}}</ref><ref>{{Cite Thejournal best|last=Renner known|first=Renato example|last2=Wolf |first2=Ramona |date=2023 |title=Quantum Advantage in Cryptography |url=https://doi.org/10.2514/1.J062267 |journal=AIAA Journal |volume=61 |issue=5 |pages=1895–1910 |doi=10.2514/1.J062267 |issn=0001-1452}}</ref> Historically defined as the practice of encoding messages, a concept now referred to as encryption, cryptography plays a crucial role in the secure processing, storage, and transmission of information across various domains. One aspect of quantum cryptography is [[quantum key distribution]] (QKD), which offers an [[Information-theoretic security|information-theoretically secure]] solution to the [[key exchange]] problem. The advantage of quantum cryptography lies in the fact that it allows the completion of various cryptographic tasks that are proven or conjectured to be impossible using only classical (i.e. non-quantum) communication. Furthermore, quantum cryptography affords the authentication of messages, which allows the legitimates parties to prove that the messages wre not wiretaped during transmission.<ref>{{Cite journal |last=Gisin |first=Nicolas |last2=Ribordy |first2=Grégoire |last3=Tittel |first3=Wolfgang |last4=Zbinden |first4=Hugo |date=2002-03-08 |title=Quantum cryptography |url=https://link.aps.org/doi/10.1103/RevModPhys.74.145 |journal=Reviews of Modern Physics |volume=74 |issue=1 |pages=145–195 |doi=10.1103/RevModPhys.74.145}}</ref> For example, in a cryptographic set-up, it is [[No-cloning theorem|impossible to copy]] with perfect fidelity, the data encoded in a [[quantum state]]. If one attempts to read the encoded data, the quantum state will be changed due to [[wave function collapse]] ([[no-cloning theorem]]). This could be used to detect eavesdropping in [[QKD schemes, or in quantum keycommunication distribution]]links and networks. These advantages have significantly influenced the evolution of quantum cryptography, making it practical in today's digital age, where devices are increasingly interconnected and cyberattacks have become more sophisticated. As such quantum cryptography is a critical component in the advancement of a quantum internet, as it establishes robust mechanisms to ensure the long-term privacy and integrity of digital communications and systems.<ref>{{Cite journal |last=Mitra |first=Saptarshi |last2=Jana |first2=Bappaditya |last3=Bhattacharya |first3=Supratim |last4=Pal |first4=Prashnatita |last5=Poray |first5=Jayanta |date=November 2017 |title=Quantum cryptography: Overview, security issues and future challenges |url=https://ieeexplore.ieee.org/abstract/document/8350006 |journal=2017 4th International Conference on Opto-Electronics and Applied Optics (QKDOptronix) |pages=1–7 |doi=10.1109/OPTRONIX.2017.8350006}}</ref>

== History ==

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== Applications ==

Quantum cryptography is a general subject that covers a broad range of cryptographic practices and protocols. SomeWhile ofencryption techniques are widely recognized and understood, a significant challenge remains in the mostsecure distribution of shared keys, often referred to as key establishment or key agreement. [[Quantum key distribution|Quantum Key Distribution]] (QKD) aims to address this particular challenge. Below, we explore various notable applicationsmethodologies and protocolsapplications arecurrently discussedemployed belowin quantum cryptography. {{Main|Quantum key distribution}}

=== Quantum key distribution ===

{{Main|Quantum key distribution}}

The best-known and developed application of quantum cryptography is [[Quantum key distribution|QKD]], which is the process of using quantum communication to establish a shared key between two parties (Alice and Bob, for example) without a third party (Eve) learning anything about that key, even if Eve can eavesdrop on all communication between Alice and Bob. If Eve tries to learn information about the key being established, discrepancies will arise causing Alice and Bob to notice. Once the key is established, it is then typically used for [[encrypted]] communication using classical techniques. For instance, the exchanged key could be used for [[symmetric cryptography]] (e.g. [[one-time pad]]).

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=== Deprecation of quantum key distributions from governmental institutions ===

Because of the practical problems with quantum key distribution, some governmental organizations recommend the use of post-quantum cryptography (quantum resistant cryptography) instead. For example, the US [[National Security Agency]],<ref name="NSA">{{cite web |title=Quantum Key Distribution (QKD) and Quantum Cryptography (QC) |url=https://www.nsa.gov/Cybersecurity/Quantum-Key-Distribution-QKD-and-Quantum-Cryptography-QC/ |publisher=[[National Security Agency]] |access-date=16 July 2022}} {{PD-notice}}</ref> [[European Union Agency for Cybersecurity]] of EU (ENISA),<ref>Post-Quantum Cryptography: Current state and quantum mitigation, Section 6 "Conclusion" [https://www.enisa.europa.eu/publications/post-quantum-cryptography-current-state-and-quantum-mitigation]</ref> UK's [[National Cyber Security Centre (United Kingdom)|National Cyber Security Centre]],<ref>[https://www.ncsc.gov.uk/whitepaper/quantum-security-technologies Quantum security technologies]</ref> French Secretariat for Defense and Security (ANSSI), <ref> Should Quantum Key Distribution be Used for Secure Communications? [https://cyber.gouv.fr/en/publications/should-quantum-key-distribution-be-used-secure-communications Should Quantum Key Distribution be Used for Secure Communications?]</ref> and German Federal Office for Information Security (BSI)<ref>{{cite web | url=https://www.bsi.bund.de/EN/Themen/Unternehmen-und-Organisationen/Informationen-und-Empfehlungen/Quantentechnologien-und-Post-Quanten-Kryptografie/Quantenkryptografie/quantenkryptografie.html | title=Quantum Cryptography }}</ref> recommend post-quantum cryptography.

For example, the US National Security Agency addresses five issues:<ref name="NSA" />