| Cryptography | |
|---|---|
| Name | Cryptography |
| Caption | Quantum key distribution demonstration |
| Field | Cryptography / Quantum Physics |
| Introduced | Classical ciphers ancient; quantum protocols since 1980s |
| Researchers | Charles Bennett, Gilles Brassard, Artur Ekert, Peter Shor, Lov Grover |
| Institutions | IBM, Google, National Institute of Standards and Technology, University of Cambridge, MIT |
Cryptography
Cryptography is the study and practice of securing information by transforming it to resist unauthorized access. In the context of Quantum physics, cryptography both faces novel threats from quantum algorithms and gains new protocols that leverage quantum phenomena to provide information-theoretic security. Quantum-enabled cryptography reshapes assumptions underlying confidentiality, integrity, and authentication in modern Computer security.
Cryptography historically relies on mathematical hardness assumptions such as the difficulty of factoring integers or computing discrete logarithms, problems central to schemes like RSA and elliptic-curve cryptography (ECC). Developments in Quantum computing—including algorithmic breakthroughs such as Shor's algorithm and Grover's algorithm—threaten these assumptions by providing asymptotic and practical speedups. Conversely, quantum physics enables novel cryptographic primitives like Quantum key distribution (QKD) and quantum-secure randomness expansion that exploit entanglement and quantum measurement. Research spans theoretical computer science, experimental physics, and standards bodies including National Institute of Standards and Technology (NIST) post-quantum efforts.
Classical public-key systems such as RSA, Diffie–Hellman, and ECC are vulnerable to polynomial-time attacks by quantum computers using Shor's algorithm. Symmetric-key systems (e.g., AES) face only quadratic speedups via Grover's algorithm, affecting key-length recommendations. The prospect of "store now, decrypt later" adversaries has motivated agencies and companies—NSA, ENISA, Google—to plan migrations. Cryptanalysis research connects to complexity-theory concepts such as BQP and hardness assumptions like lattice problems exemplified by LWE.
Quantum cryptography applies quantum mechanics to cryptographic tasks. The canonical protocol, BB84, introduced by Charles Bennett and Gilles Brassard, uses non-orthogonal quantum states to establish a shared key with eavesdropper detection. Entanglement-based protocols such as E91 by Artur Ekert utilize Bell inequality violations to certify secrecy. Other primitives include device-independent QKD, quantum coin flipping, and quantum bit commitment (which faces no-go results under certain assumptions). Implementations rely on quantum optics platforms developed in laboratories at institutions like University of Geneva and companies such as ID Quantique. Security proofs often invoke concepts from Quantum information theory, including trace distance, monogamy of entanglement, and the no-cloning theorem.
Post-quantum cryptography aims to build classical algorithms secure against quantum adversaries. NIST's ongoing standardization competition evaluates schemes based on lattices (e.g., CRYSTALS-Kyber, CRYSTALS-Dilithium), code-based systems (e.g., McEliece cryptosystem), multivariate quadratic equations, and hash-based signatures (e.g., SPHINCS+). Security reductions relate to problems such as SIS and LWE. Practical adoption involves libraries like OpenSSL and protocol updates in standards such as TLS. Hybrid approaches combine classical and post-quantum primitives to hedge migration risks.
Real-world deployment of quantum and post-quantum cryptography encounters engineering and physics constraints. QKD systems demand low-loss optical fibers, free-space links, or satellite relays as demonstrated by the Micius (satellite) mission. Practical devices face side-channel vulnerabilities—timing, detector blinding, and implementation flaws—addressed by device-independent protocols and rigorous characterization in labs at NIST and university groups. Quantum hardware development by IBM, Google, and Rigetti informs cryptanalytic capabilities while photonic companies such as ID Quantique and Toshiba drive QKD commercialization. Interoperability, key management, and integration with existing Public Key Infrastructure present further deployment challenges.
Quantum-enhanced cryptography applies to secure communications, key distribution for critical infrastructure, and quantum random number generation used in banking and governance. QKD networks have been fielded in metropolitan deployments like the SECOQC network and integrated into testbeds such as the UK Quantum Network. Security models vary from information-theoretic (unconditional) security in ideal QKD to computational security in post-quantum schemes; cryptographic protocols are analyzed under composable frameworks like Universal composability adapted to quantum settings. Standards and certification processes by bodies including ETSI and ISO/IEC guide practical assurance and interoperability.
Future research emphasizes building quantum networks (the Quantum Internet), scalable QKD, quantum repeaters, and hybrid classical-quantum architectures. Advances in quantum error correction, fault-tolerant quantum computing, and new algorithms will reshape threat models. Continued work on formal security proofs, standardization of post-quantum primitives, and mitigation of implementation vulnerabilities will be central. Collaborative initiatives span academia, industry, and government—including projects at CERN, European Commission research programs, and national quantum initiatives—integrating Quantum information science into the broader cybersecurity ecosystem. Category:Quantum cryptography