The concatenation of encryption and decryption can be interpreted as data transmission over a noisy communication channel. In this work, we use finite blocklength methods (normal approximation and random coding union bound) as well as asymptotics to show that ciphertext and key sizes of the state-of-the-art post-quantum secure key encapsulation mechanism (KEM) Kyber can be reduced without compromising the security of the scheme. We show that in the asymptotic regime, it is possible to reduce the sizes of ciphertexts and secret keys by 25% for the parameter set Kyber1024 while keeping the bitrate at 1 as proposed in the original scheme. For a single Kyber encryption block used to share a 256-bit AES key, we furthermore show that reductions in ciphertext size of 39% and 33% are possible for Kyber1024 and Kyber512, respectively.
The concatenation of encryption and decryption can be interpreted as data transmission over a noisy communication channel. In this work, we use finite blocklength methods (normal approximation and random coding union bound) as well as asymptotics to show that ciphertext and key sizes of the state-of-the-art post-quantum secure key encapsulation mechanism (KEM) Kyber can be reduced without compromising the security of the scheme. We show that in the asymptotic regime, it is possible to reduce the sizes of ciphertexts and secret keys by 25% for the parameter set Kyber1024 while keeping the bitrate at 1 as proposed in the original scheme. For a single Kyber encryption block used to share a 256-bit AES key, we furthermore show that reductions in ciphertext size of 39% and 33% are possible for Kyber1024 and Kyber512, respectively.
The NTRU lattice is a promising candidate to construct practical cryptosystems, in particular key encapsulation mechanism (KEM), resistant to quantum computing attacks. Nevertheless, there are still some inherent obstacles to NTRU-based KEM schemes in having integrated performance, taking security, bandwidth, error probability, and computational efficiency \emph{as a whole}, that is as good as and even better than their \{R,M\}LWE-based counterparts. In this work, we solve this problem by presenting a new family of NTRU-based KEM schemes, referred to as CTRU and CNTR. By bridging low-dimensional lattice codes and high-dimensional NTRU-lattice-based cryptography with careful design and analysis, to the best of our knowledge CTRU and CNTR are the first NTRU-based KEM schemes with scalable ciphertext compression via only one \emph{single} ciphertext polynomial, and are the first that could outperform \{R,M\}LWE-based KEM schemes in integrated performance. For instance, compared to Kyber that is currently the only standardized KEM by NIST, on the recommended parameter set CNTR-768 has about 12% smaller ciphertext size while encapsulating 384-bit keys compared to the fixed 256-bit key size of Kyber, security strengthened by (8,7) bits for classical and quantum security respectively, and significantly lower error probability (2−230 of CNTR-768 vs. 2−164 of Kyber-768). In comparison with the state-of-the-art AVX2 implementation of Kyber-768, CNTR-768 is faster by 1.9X in KeyGen, 2.6X in Encaps, and 1.2X in Decaps, respectively. When compared to the NIST Round 3 finalist NTRU-HRSS, our CNTR-768 has about 15% smaller ciphertext size, and the security is strengthened by (55,49) bits for classical and quantum security respectively. As for the AVX2 implementation, CNTR-768 is faster than NTRU-HRSS by 19X in KeyGen, 2.3X in Encaps, and 1.6X in Decaps, respectively.
The widespread use of Internet of Things devices alongside advances in quantum computing presents urgent challenges for secure communication. RSA and ECC have become inadequate, prompting the need for Post-quantum Cryptography (PQC). This work introduces a novel reconciliation-based Module-LWE key exchange protocol that eliminates the traditional encapsulation-decapsulation structure in schemes like Kyber.KE, thereby reducing computational cycles, communication size, and memory footprint. Unlike Kyber and NewHope, the proposed design employs modular rounding with Peikert reconciliation, optimizing the entire key exchange process without requiring additional randomness or ciphertext transmission. By leveraging Peikert’s error reconciliation technique and modular rounding, the proposed protocol achieves a 15% reduction in computational cycles, a 78-byte reduction in communication size, and a 10% decrease in memory usage. Using Open Quantum Safe (OQS) benchmark data, we evaluate performance across Kyber512, Kyber768, and Kyber1024 levels, demonstrating the protocol’s superior energy efficiency and lightweight design. These improvements position our protocol as a secure, efficient, and scalable solution for post-quantum key exchange in resource-constrained environments such as embedded systems and IoT networks.
This paper proposes a new generic Encrypt-thenMAC (EtM) transformation for constructing IND-CCA secure Key Encapsulation Mechanisms (KEMs) in the post-quantum setting. The transformation builds on a public-key encryption scheme satisfying one-wayness under plaintext-checking attacks (OW-PCA) and an existentially unforgeable MAC, and formally achieves tight IND-CCA security in the random oracle model via a rigorous security reduction. Unlike the widely used FujisakiOkamoto (FO) transformation, our approach eliminates the need for ciphertext re-encryption during decapsulation-a major source of computational overhead and side-channel vulnerability in lattice-based implementations. We instantiate the transformation using the ML-KEM (FIPS 203) subroutine, yielding the ML-KEM-EtM variant. Experimental results show that ML-KEMEtM reduces decapsulation cycle counts by72−79%across security levels, with only a modest increase in encapsulation cost(1.8−7.3%)and ciphertext size(1.0−2.1%). The scheme thus offers a practical and efficient a lternative to F O-based KEMs, especially in performance-critical scenarios such as post-quantum TLS handshakes, where decapsulation efficiency is paramount.
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.
Recently, American National Institute of Standards and Technology (NIST) announced Kyber as the first KEM candidate to be standardized. The security of Kyber is based on the modular learning with errors (MLWE) problem, which achieves excellent efficiency and size. This work proposes an improved key mismatch on Kyber, which can reduce the number of queries required to recover the secret key. We first transform the problem of finding a certain parameter of ciphertexts into a quantum ordered search problem. Then we give the procedure of finding the value of a parameter in the ciphertexts by the quantum method. Finally, we instantiate this attack method on Kyber512, Kyber768 and Kyber1024. Compared with the existing attack algorithm, our improved attack reduces the number of queries for Kyber512, Kyber768 and Kyber1024 by 63%, 59% and 45%, respectively.
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,