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International Journal of Creative and Open Research in Engineering and Management

Layered Post-Quantum Cryptography: A Dual-Encryption Approach to Mitigate Quantum Threats

Vijay Subhash Katta, DIWAKAR SHRIVASTAVA, Deepanshi Kushwah Deepanshi Kushwah, Deepak Kushwah Deepak Kushwah

Published Jun 27, 2026• 0 citations
Publisher

Abstract

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.

DOI
10.55041/ijcope.v2i6.338

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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 rapid advancement of quantum computing poses a serious threat to traditional cryptographic systems such as RSA and Elliptic Curve Cryptography (ECC), which rely on computational difficulty for security. Quantum algorithms like Shor’s and Grover’s have the potential to break or weaken these methods, putting modern communication systems at risk. To address this challenge, this work presents a quantum-safe com-munication framework that combines the BB84 Quantum Key Distribution (QKD) protocol with Post-Quantum Cryptography (PQC) techniques, aiming to ensure secure data exchange in the presence of quantum-capable adversaries. In this system, the BB84 protocol is simulated to enable secure key exchange between two parties over a virtual quantum channel. The generated key is refined through processes such as basis matching, error correction, and privacy amplification using SHA-256 to ensure reliability and secrecy. For secur-ing communication, One-Time Pad (OTP) encryption is used alongside HMAC-SHA3-256 to provide both confidentiality and message integrity. Additionally, file encryption is handled using the XChaCha20-Poly1305 algorithm, selected for its efficiency and strong protection against potential vulnerabilities like nonce reuse. To further enhance security, the framework integrates a hybrid key management approach using the Kyber-512 Key Encapsulation Mechanism (KEM) combined with a Key Deriva-tion Function (KDF), merging classical and quantum-resistant techniques. Experimental results demonstrate the effectiveness of the system, achieving a Quantum Bit Error Rate (QBER) of 2.5% and successful performance in both message and file en-cryption. Overall, this work contributes toward the development of practical and resilient communication systems designed for the emerging quantum era.
The emergence of quantum computing poses a fundamental threat to current public key cryptographic systems. This threat is necessitating a transition to quantum resistant cryptographic alternatives in all the applications. In this work, we present the implementation of a practical hybrid end-to-end encryption system that combines classical and post-quantum cryptographic primitives to achieve both security and efficiency. Our system employs CRYSTALS-Kyber, a NIST-standardized lattice-based key encapsulation mechanism, for quantum-safe key exchange, coupled with AES-256-GCM for efficient authenticated symmetric encryption and SHA-256 for deterministic key derivation. The architecture follows a zero-trust model where a relay server facilitates communication without accessing plaintext messages or cryptographic keys. All encryption and decryption operations occur exclusively at client endpoints. The system demonstrates that NIST standardized post-quantum cryptography can be effectively integrated into practical messaging systems with acceptable performance characteristics, offering protection against both classical and quantum adversaries. As our focus is on implementation rather than on novelty, we also provide an open-source implementation to facilitate reproducibility and further research in post quantum secure communication systems.
The Hybrid approach in Quantum Cryptography creates adaptable security model which provides the safest Communication in the emerging quantum era. The development of quantum computing raise questions about the long-term security. Traditional algorithms, such as RSA, ECC, and Diffie-Hellman, which is seemed computationally secure but it can be effectively solved by quantum algorithms such as Shor's and Grover's. This problem leads to the origination of two key trends in current studies, namely Post-Quantum Cryptography (PQC), designing mathematical approaches to encryption resistant to quantum attacks; Quantum Key Distribution (QKD) using the principles of quantum mechanics to assure security in communications. Accordingly, this research proposes a hybrid security framework including reliable data encryption and authentication using PQC, combined with the safe key- exchange method of QKD. The model is implemented in Python, Qiskit, and PQClean's Kyber and Dilithium algorithms to show how these two paradigms can cooperate toward quantum- resilient communication. To present the system performance, key exchange efficiency, computational overhead, and security strength have been considered. According to the results, this hybrid approach gives superior defense against quantum threats while maintaining practical effectiveness for real-world applications such as cloud security, 6G networks, and the Internet of Things.
Classical public-key cryptography, mainly RSA, is at risk from the emergence of quantum computers. A complete shift to Post-Quantum Cryptography (PQC) faces vulnerabilities due to implementation and trust issues, despite NIST's approval of standards such as ML-KEM (Kyber). This paper presented a performance and bandwidth trade-off study of a proposed Hybrid Key Encapsulation Mechanism that fused the NIST-standardized ML-KEM-768 (FIPS 203) with the traditional RSA-3072. Two separate secret keys S1 and S2 were produced and encapsulated utilizing both classical and post-quantum public keys in our dual-layered model. In order to create a strong session key that ensures trust transition and backward compatibility with current network infrastructures, these secrets were then combined using a Hybrid Key Derivation Function (HKDF). In comparison to standalone systems, the study assessed the computational cost and communication latency brought about by this hybrid overhead. According to experimental data, the hybrid architecture offers a crucial security fail-safe against both classical flaws and future quantum threats without prohibitively high performance, even though it increases ciphertext size.
The need for secure communication in the advent of fully developed quantum computers is underscored by the ongoing standardization of Post-Quantum Cryptography algorithms (PQC). However, due to the complexity and long processing time of PQC algorithms, it is impractical to use them directly in most applications. Therefore, a practical implementation, especially in applications that may be vulnerable to quantum attacks, is essential. This paper proposes PQC-based and PQC-AES (Advanced Encryption Standard) hybrid Public Key Encryption (PKE) protocols to secure the communication of application data transmitted between two parties. The parties securely exchange their PQC keys using a PQC Key Encapsulation Mechanism (KEM) scheme. In the PQC-based PKE, the exchanged PQC public keys (asymmetric key cryptography) are used to encrypt data for network transmission. To decrypt the encrypted data, each party uses their private PQC secret key, known only to them, enabling secure end-to-end communication. In the PQC-AES hybrid PKE, a two-way shared secret key is used to generate a symmetric key (symmetric key cryptography) for encryption and decryption. The performance of the proposed protocols is evaluated through experiments with PQC algorithms in a client-server file transfer application. The evaluation results highlight the necessity of considering security, latency, and other metrics when implementing PQC algorithms in various applications. It is confirmed that KYBER1024 and BIKE-L1 achieved similar throughput in comparison to using the conventional AES-256 key encryption algorithm without extensive overheads in the wireless network for a smaller load (e.g., 1 KB size), while the PQC-AES hybrid cryptography protocol may be suitable for applications where the data size is larger,
Abstract - In the emerging era of quantum computing, traditional cryptographic algorithms such as RSA and Elliptic Curve Cryptography (ECC) are at risk from quantum-based attacks. These developments pose a significant threat to secure network communication systems that rely on classical key exchange mechanisms. To overcome this challenge, the proposed work introduces a Hybrid Quantum-Resistant Key Exchange Protocol that combines the strengths of both classical andpost-quantum cryptographic algorithms. The hybrid approach integrates Elliptic Curve Dif ie–Hellman (ECDH) with alattice-based post-quantum algorithm, Kyber, to establish a shared session key between communicating entities. This sharedkeyisthen utilized for symmetric encryption using AES to ensure confidentiality and data integrity. The system is implementedusingPython socket programming to demonstrate secure data transmission between client and server. Performance is analyzedinterms of key generation time, encryption and decryption speed, key size, and computational ef iciency. The results validatethatthe proposed hybrid model provides enhanced resistance against quantum attacks while maintaining acceptable performance, making it suitable for future secure communication systems. Keywords - elliptic curve dif ie–hellman, hybrid key exchange, kyber, post-quantum cryptography, quantum computing.