Authenticated key exchange mechanisms instantiated with cryptosystems
based on integer factorization, finite field discrete log, or elliptic
curve discrete log, are believed to be secure now but are vulnerable
to a harvest-then-decrypt attack where an attacker who cannot
currently break the mechanism records the traffic anyway, then
decrypts it at some point in the future when quantum computers become
available. The Quantum-safe Hybrid approach is a modular design,
allowing any authenticated key exchange mechanism to be protected
against the harvest-then-decrypt attack by exchanging additional
secret material protected with an ephemeral key for a quantum-safe
public key cryptographic algorithm and including that secret material
in the Key Derivation Function (KDF) run at the end of the key
exchange. This approach has been proposed in TLS as the Quantum-safe
Hybrid handshake mechanism for Transport Layer Security protocol
(QSH_TLS). This document provides a guideline to criteria for
selecting public key encryption algorithms approved for experimental
use in the quantum safe hybrid setting.
Authenticated key exchange mechanisms instantiated with cryptosystems
based on integer factorization, finite field discrete log, or elliptic
curve discrete log, are believed to be secure now but are vulnerable
to a harvest-then-decrypt attack where an attacker who cannot
currently break the mechanism records the traffic anyway, then
decrypts it at some point in the future when quantum computers become
available. The Quantum-safe Hybrid approach is a modular design,
allowing any authenticated key exchange mechanism to be protected
against the harvest-then-decrypt attack by exchanging additional
secret material protected with an ephemeral key for a quantum-safe
public key cryptographic algorithm and including that secret material
in the Key Derivation Function (KDF) run at the end of the key
exchange. This approach has been proposed in TLS as the Quantum-safe
Hybrid handshake mechanism for Transport Layer Security protocol
(QSH_TLS). This document provides a guideline to criteria for
selecting public key encryption algorithms approved for experimental
use in the quantum safe hybrid setting.
Currently deployed public-key infrastructure faces an imminent threat in the face of quantum computers. It is expected that, given sufficiently large and reliable quantum computers, dedicated quantum algorithms such as Shor's algorithm [1] will completely break cryptographic schemes whose security is based on the discrete logarithm and integer factorisation problems. This includes widely deployed cryptographic algorithms such as RSA, Diffie-Hellman and elliptic-curve based approaches which underpin the security of existing electronic communications. Therefore, the secrecy of highly sensitive information currently being exchanged is under significant threat as messages can be recorded in bulk and decrypted in the future in so-called harvest-and-decrypt attacks.
Cryptography, the practice of concealing messages for private exchange, has evolved significantly to address the challenges posed by new communication methods. In today`s digital world, cryptography has become the cornerstone of cybersecurity, using advanced mathematics like number theory and computational complexity to protect digital information through algorithms. The upcoming arrival of quantum computers poses a serious threat to traditional cryptographic methods, especially those based on asymmetric key cryptography. Quantum Safe Cryptography (QSC) represents the next step in information security, designed to develop cryptographic systems that can withstand attacks from both quantum and classical computers. As quantum computing moves from theory to reality, it`s becoming clear that current cryptographic methods based on integer factorization and discrete logarithm problems are vulnerable to quantum algorithms like Shor`s algorithm. This study highlights the security risks that quantum computing poses to existing encryption methods and proposes a comprehensive approach to quantum-safe cryptography. The transition to quantum-resistant algorithms involves replacing vulnerable cryptographic systems with alternatives that can resist quantum computational attacks. Current analysis shows that while asymmetric key cryptography faces immediate vulnerability, symmetric key algorithms and hash functions remain relatively secure in the near term with appropriate adjustments. Quantum cryptography, which directly uses quantum mechanical principles, offers highly secure encryption mechanisms, notably Quantum Key Distribution (QKD). This research aims to enhance the security of digital infrastructure against quantum threats by evaluating hybrid cryptographic implementations that combine classical and quantum-resistant approaches for optimal security.
Quantum computing offers major computational advances but threatens modern public-key cryptography. Classical algorithms such as RSA, Diffie–Hellman (DH), and Elliptic Curve Cryptography (ECC) are vulnerable to quantum attacks, particularly Shor’s algorithm. As large-scale quantum capabilities emerge, post-quantum cryptography (PQC) has become essential to ensure future data confidentiality, integrity, and authentication. This paper discusses the need to replace classical cryptography, explores quantum-safe solutions, and examines challenges in large-scale migration. PQC is critical across government, critical infrastructure, finance, healthcare, telecommunications, IoT, autonomous vehicles, and 6G networks. A key concern is “harvest-now, decrypt-later” attacks, where encrypted data is stored today for future quantum decryption. The study analyzes classical cryptographic vulnerabilities and reviews major PQC families: lattice-based, hash-based, code-based, multivariate-based, and isogeny-based schemes, highlighting the ongoing NIST standardization efforts. It proposes a migration framework including quantum-readiness assessment, algorithm selection, hybrid implementation, and performance evaluation. Results show that although PQC introduces higher computational complexity, optimized implementations can support real-time applications with reasonable overhead. Among PQC approaches, lattice-based schemes appear most mature and balanced in terms of security and key size. The paper concludes that quantum-safe cryptography is a necessary evolution requiring continuous monitoring, adaptable systems, and alignment with emerging standards.
Today's information society relies on cryptography to achieve security goals such as confidentiality, integrity, authentication, and non-repudiation for digital communications. Here, public-key cryptosystems play a pivotal role to share encryption keys and create digital signatures. However, quantum computers threaten the security of traditional public-key cryptosystems as they can tame computational problems underlying the schemes, i.e., discrete logarithm and integer factorization. The prospective arrival of capable-enough quantum computers already threatens today's secret communication in terms of their long-term secrecy when stored to be later decrypted. Therefore, researchers strive to develop and deploy alternative schemes.In this work, we evaluate a key exchange protocol based on combining public-key schemes with physical-layer security, anticipating the prospect of quantum attacks: If a powerful quantum attacker cannot immediately obtain a private key, legitimate parties have a window of short-term secrecy to perform a physical-layer jamming key exchange (JKE) to establish a long-term shared secret. Thereby, the protocol constraints the computation time available to the attacker to break the employed public-key cryptography. In this paper, we outline the protocol, discuss its security, and point out challenges to be resolved.
With quantum computing technology getting better and faster, many current encryption methods may no longer be safe. One major concern is the SNDL or “Store Now, Decrypt Later” attack [1]. In this scenario, attackers collect and store encrypted data now, planning to decrypt it in the future once quantum computers become strong enough. This is especially risky for public-key systems like RSA and Elliptic Curve Cryptography [2]. This research focuses on how to keep data safe during the time before post-quantum cryptographic standards are fully rolled out. We review and compare several existing encryption methods. RSA is discussed in terms of its known weaknesses and how it is still used in some hybrid systems. AES, especially AES-256, is looked at for its better performance and stronger protection even in a post-quantum world. We also explore hybrid systems that mix different methods to cover up each other's weak spots. Lastly, we present a new layered hybrid model that brings together classical and post-quantum techniques. The proposed system uses PQC for authentication, Quantum Key Distribution for secure key exchange, and AES for encrypting the actual data.
The threats are existential to the traditional cryptosystems of public keys, including RSA, Diffie-Hellman, and elliptic curve cryptography (ECC), due to the rapid progress in quantum computing. Such algorithms as the Shor and Grover algorithms prove that as soon as large scale quantum computers are achieved, these classical cryptographic protocols will not provide any privacy and integrity to online communication. This has created an emergency to find post-quantum cryptography (PQC), or quantum-safe cryptography, which will resist attacks by both classical and quantum attackers. The paper is a review of the latest research and development in post-quantum cryptographic algorithms and their implementation in current security systems. We organize quantum-safe methods into significant organizations such as lattice-based, hash-based, multivariate polynomial-based and code-based encrypted communications. Each type has been evaluated critically based on computational efficiency, key sizes, speed of encryption/decryption and security proofs. The survey also examines the current standardization activities happening in the world and especially the U.S. National Institute of Standards and Technology (NIST) PQC competition, which lists candidate algorithms that have advanced to standard adoption. Besides this, the paper addresses hybrid cryptographic designs that use both classical and post-quantum bases in ensuring a seamless migration in the transition phase. Internet security protocols like TLS, VPNs and blockchain consensus as applications of PQC are examined in detail. Lastly, we pinpoint open research issues, which include creating lightweight PQC to support resource-constrained IoT devices, balancing performance and strong security assurances, and interoperability between the new PQC algorithms and existing infrastructures. Through detailed survey we inform the future of researchers, practitioners, and policymakers on the preparation of the post-quantum era of secure digital communications.