Quantum key distribution (QKD) allows Alice and Bob to share a secret key with proven information-theoretic security. Composability-based security proofs for QKD ensure that using the established key to encrypt a message using a one-time-pad encryption system, will result in information-theoretic secrecy for the communication. In this paper, we consider the problem of using a QKD established key with a secure symmetrickey based encryption system with computational security, and use an extension of the framework of hybrid encryption to prove security of the composition. We use an extension of the original framework of hybrid encryption to correlated randomness setting (Sharifian et al. in ISIT 2021) and propose a quantum-enabled Key Encapsulation Mechanism (qKEM) that is used to construct a quantum-enabled hybrid encryption ($q H E$) system, and prove a composition theorem for the security of the qHE. We construct a qKEM with proven security using an existing QKD (Portmann et al. in Rev. of Mod. Physics 2022). Using this qKEM with a secure Data Encapsulation Mechanism (DEM), that can be constructed using a one-time symmetric key encryption scheme, results in an efficient encryption scheme for unrestricted length messages with proved security against an adversary with access to (efficient) quantum computations. Thus a key-efficient post-quantum secure encryption with proved security and without using any computational assumptions.
Quantum key distribution (QKD) allows Alice and Bob to share a secret key with proven information-theoretic security. Composability-based security proofs for QKD ensure that using the established key to encrypt a message using a one-time-pad encryption system, will result in information-theoretic secrecy for the communication. In this paper, we consider the problem of using a QKD established key with a secure symmetrickey based encryption system with computational security, and use an extension of the framework of hybrid encryption to prove security of the composition. We use an extension of the original framework of hybrid encryption to correlated randomness setting (Sharifian et al. in ISIT 2021) and propose a quantum-enabled Key Encapsulation Mechanism (qKEM) that is used to construct a quantum-enabled hybrid encryption (qHE) system, and prove a composition theorem for the security of the qHE. We construct a qKEM with proven security using an existing QKD (Portmann et al. in Rev. of Mod. Physics 2022). Using this qKEM with a secure Data Encapsulation Mechanism (DEM), that can be constructed using a one-time symmetric key encryption scheme, results in an efficient encryption scheme for unrestricted length messages with proved security against an adversary with access to (efficient) quantum computations. Thus a key-efficient post-quantum secure encryption with proved security and without using any computational assumptions.
A hybrid encryption scheme consists of a public-key part called the key encapsulation mechanism (KEM), that is used to generate and establish a shared secret key between two parties, and a (symmetric) secret-key part called the data encapsulation mechanism (DEM) that encrypts the data using the shared key. Hybrid encryption schemes are widely used for securing Internet communication. In this paper, we initiate the study of hybrid encryption in preprocessing model which assumes access to initial correlated variables by all parties (including the eavesdropper), and define information-theoretic KEM (iKEM) that together with a (computationally) secure DEM, results in a hybrid encryption scheme in preprocessing model. We define security of each building block, and prove a composition theorem that guarantees (computational) q-chosen-plaintext attack (CPA) security of the hybrid encryption system if the iKEM and the DEM satisfy q-chosen-encapsulation attack security and one-time security, respectively. We show that an iKEM can be realized by an information-theoretic one-way secret key agreement (OW-SKA) protocol where a single message is transmitted from Alice to Bob, with a new security definition that allowsqqueries to Alice. Using a OW-SKA that satisfies this new definition of security, effectively allows the established secret key to be used with a onetime symmetric key encryption system that can be implemented, for example, by XORing the output of a (computationally) secure pseudorandom generator with the message, to provide secure encryption ofqarbitrary messages (polynomially bounded length). We discuss our results and directions for future work.
A hybrid encryption scheme uses a key encapsulation mechanism (KEM) to generate and establish a shared secret key with the decrypter, and a secret key data encapsulation mechanism (DEM) to encrypt the data using the key that is established by the DEM. The decrypter recovers the key using the ciphertext that is generated by the KEM, and uses it to decrypt the ciphertext that is generated by the DEM.We motivate and propose hybrid encryption in correlated randomness model where all participants including the eavesdropper, have access to samples of their respective correlated random variables. We define information-theoretic KEM (iKEM), and prove a composition theorem for iKEM and DEM that allows us to construct an efficient hybrid encryption system in correlated randomness model, providing post-quantum security. The construction uses an information-theoretic one-way secret key agreement (OW-SKA) protocol that satisfies a new security definition, and a one-time symmetric key encryption system that can be implemented by XORing the output of a (computationally) secure pseudorandom generator with the message. We discuss our results and directions for future work.
In contrast to classical public-key cryptosystems, where the security of encoded messages relies on on computational assumptions, Quantum Key Distribution (QKD) enables two distant parties to establish a shared secret key that, when combined with a one-time pad, provides information-theoretically secure encryption, provided that the QKD protocol is supported by a rigorous security proof. In the last decades, security proofs robust against a wide range of eavesdropping strategies have established the theoretical soundness of several QKD protocols. However, most proofs are based on idealized models of the physical systems involved in such protocols and often include assumptions that are not satisfied in practical implementations. This mismatch creates a gap between theoretical security guarantees and actual experimental realizations, making QKD protocols vulnerable to attacks. To ensure the security of real-world QKD systems, it is therefore essential to account for imperfections in security analyses. In this article, we present an overview of recent analytical and numerical developments in QKD security proofs, which provide a versatile approach for incorporating imperfections and re-establishing the security of quantum communication protocols under realistic conditions.
A hybrid encryption scheme is a public-key encryption system that consists of a public-key part called the key encapsulation mechanism (KEM), and a (symmetric) secret-key part called data encapsulation mechanism (DEM): the public-key part is used to generate a shared secret key between two parties, and the symmetric key part is used to encrypt the message using the generated key. Hybrid encryption schemes are widely used for secure communication over the Internet. In this paper, we initiate the study of hybrid encryption in preprocessing model which assumes access to initial correlated variables by all parties (including the eavesdropper). We define information-theoretic KEM (iKEM) that, together with a (computationally) secure DEM, results in a hybrid encryption scheme in preprocessing model. We define the security of each building block, and prove a composition theorem that guarantees (computational) qe-chosen plaintext (CPA) security of the hybrid encryption system if the iKEM and the DEM satisfy qe-chosen encapculation attack and one-time security, respectively. We show that iKEM can be realized by a one-way SKA (OW-SKA) protocol with a revised security definition. Using an OW-SKA that satisfies this revised definition of security effectively allows the secret key that is generated by the OW-SKA to be used with a one-time symmetric key encryption system such as XORing a pseudorandom string with the message, and provide qe-CPA security for the hybrid encryption system.We discuss our results and directions for future work.
The fast development of cyber communications, multimedia distribution, remote working have promoted the demand to transmit sensitive information through secure means in both the public and the private networks. The advent of massive quantum computers is rendering traditional cryptographic algorithms like RSA and Elliptic Curve Cryptography (ECC) insecure because they can crack the classical public-key algorithms like the Shor and Grover algorithms. This brings an immediate need of hybrid cryptographic systems, which integrate classical, quantum, and post-quantum algorithms to provide confidentiality, integrity, authentication, and future security beyond the quantum threat horizon.The paper is a proposal of a Hybrid Quantum-Post-Quantum Cryptographic Framework of transmitting files safely. It starts by aggregating files, which is a process to compress several files, images, videos, and multimedia files that users have chosen into one file to minimize redundancy and ease encryption. The AES-256 encrypted file is in GCM mode and provides confidentiality and integrity of the compressed file.The dual-layer mechanism ensures key establishment security. To begin with, Quantum Key Distribution (QKD) based on the protocols of BB84/E91 allows the Sender and the Receiver to generate a Quantum Secret Key (QSK) by exchanging quantum bits in quantum channel. Constant monitoring of the error rate facilitates automatic eavesdropping detection, and guarantees the keys generation is made when the conditions are secure, as well as the safeguarding of interception and man-in-the-middle attacks.A post-quantum layer is provided to ensure long-term security against quantum cryptanalysis, which uses Kyber, a NIST-approved lattice-based Key Encapsulation Mechanism (KEM). The Receiver creates a key pair of Kyber and disseminates the public key to the Sender. By using encapsulation, the Sender gets a PQC ciphertext and a Shared Secret (SS), with decapsulation on the Receiver side giving ensure that only participants of good faith get the same secret value.The hybridization phase consists of combining the QSK of QKD and SS of Kyber with the help of HKDF-SHA256 to obtain a Final Wrap Key (FWK). AES-GCM encrypts the key of file encryption by wrapping it with FWK which allows a secure and authenticated transfer of the key. The Sender sends four messages: encrypted file, Kyber ciphertext, wrapped AES key and the initialisation vector. At Receiver end, FWK is calculated once again with the help of QSK and SS so that the original data can be decrypted with the help of AES key.The suggested framework provides a defense-in-depth solution based on the combination of quantum security, post-quantum resilience and authenticated symmetric encryption. It can be analyzed that there is a strong resistance to classical and quantum adversaries, scalability, and compatibility with the existing communication networks. This renders the model to be appropriate to secure government communication, military systems, data exchange in healthcare environments, cloud storage and financial infrastructures. Keywords— Quantum Key Distribution (QKD), Post-Quantum Cryptography (PQC), Kyber,Key Encapsulation Mechanism (KEM), HKDF-SHA256, Quantum Secret Key (QSK), GCM Mode.
The existence of quantum computing presents an existential threat to the traditional cryptographic algorithms, and there is a need to create communication mechanisms that are fundamentally secure. In this regard, the concept of Quantum Key Distribution (QKD) provides information-theoretic security, which is founded on quantum mechanics. Nevertheless, conventional QKD protocols have serious shortcomings such as lack of distance in communication, vulnerability to side-channel attacks, and inability to support the large-scale heterogeneous network. We suggest that HQNet-QKD a Hybrid Quantum Key Distribution framework can help solve these issues by offering a more secure, scalable and future-proof key exchange framework in hybrid classical-quantum networks. To support multi-layered security, the proposed architecture is a network ensuring the smoothness of decoy-state BB84, Measurement-Device-Independent QKD (MDI-QKD), entanglement/twin-field-based QKD with verifiable Secret Sharing (VSS) and Post-Quantum Cryptography (PQC). It provides a complete methodology such as system architecture, mathematical modeling, and end-to-end key synthesis. When used over a distance of 300 km, simulation and testing have shown that HQNet-QKD can achieve up to2.7×higher secret key rate (SKR) than conventional methods, secret communication at 700 km and resilience to both quantum and classical attacks more than 96%. In addition, the framework guarantees forward secrecy, detector-side immunity, contextbound key derivation, and composability and thus resistant to current and future adversaries. It has a low-computational overhead modular design, making it trivial to deploy in a real world, in applications like quantum-secured 5G backbones, cloud data centers, critical infrastructure, and satellite-based communication systems. The findings make HQNet-QKD a new generation solution to quantum-safe secure communication and the first step towards the implementation of the quantum internet.