To ensure confidentiality and integrity in the era of quantum computing, most post-quantum cryptographic schemes are designed to achieve either encryption or digital signature functionalities separately. Although a few signcryption schemes exist that combine these operations into a single, more efficient process, they typically rely on complex vector, matrix, or polynomial-based structures. In this work, a novel post-quantum public-key encryption and signature (PQES) scheme based entirely on scalar integer operations is presented. The proposed scheme employs a simplified structure where the ciphertext, keys, and core cryptographic operations are defined over scalar integers modulo n, significantly reducing computational and memory overhead. By avoiding high-dimensional lattices or ring-based constructions, the PQES approach enhances implementability on constrained devices while maintaining strong security properties. The design is inspired by modified learning-with-errors (LWE) assumptions, adapted to scalar settings, making it suitable for post-quantum applications. Security and performance evaluations, achieving a signcryption time of 0.0007 s and an unsigncryption time of 0.0011 s, demonstrate that the scheme achieves a practical balance between efficiency and resistance to quantum attacks.
To ensure confidentiality and integrity in the era of quantum computing, most post-quantum cryptographic schemes are designed to achieve either encryption or digital signature functionalities separately. Although a few signcryption schemes exist that combine these operations into a single, more efficient process, they typically rely on complex vector, matrix, or polynomial-based structures. In this work, a novel post-quantum public-key encryption and signature (PQES) scheme based entirely on scalar integer operations is presented. The proposed scheme employs a simplified structure where the ciphertext, keys, and core cryptographic operations are defined over scalar integers modulo n, significantly reducing computational and memory overhead. By avoiding high-dimensional lattices or ring-based constructions, the PQES approach enhances implementability on constrained devices while maintaining strong security properties. The design is inspired by modified learning-with-errors (LWE) assumptions, adapted to scalar settings, making it suitable for post-quantum applications. Security and performance evaluations, achieving a signcryption time of 0.0007 s and an unsigncryption time of 0.0011 s, demonstrate that the scheme achieves a practical balance between efficiency and resistance to quantum attacks.
In this work, we introduce a novel post-quantum public key encryption scheme over integers, leveraging a hybrid approach that combines large random numbers with the Learning With Errors (LWE) system. The scheme addresses the security challenges posed by quantum computing advancements, aiming to provide a robust solution resistant to quantum-based attacks. By using the unknown random number hardness assumption with enhancements to the traditional LWE framework and operating directly on integers, this approach ensures a high level of cryptographic security while maintaining computational efficiency. Extensive theoretical and experimental analyses demonstrate that the proposed encryption system achieves state-of-the-art performance: encryption execution time as low as2.45×10−5seconds, decryption time of4.47×10−5seconds, and an integrity check time of5.30×10−5seconds. Moreover, the ciphertext size is reduced to only 1330 bits while maintaining a 256 -bit security level, representing a significant reduction in storage requirements compared to conventional lattice-based approaches. These results confirm that our scheme not only provides strong quantum-resistant security guarantees but also delivers excellent efficiency and scalability, making it a viable candidate for secure communications in bandwidth-limited and resource-constrained environments in the quantum era.
A signcryption scheme provides both the function of digital signature and encryption scheme at the same time. Additionally, it has lower cost than traditional sign-then-encrypt or encrypt-then-sign approaches. Many useful applications have been found where confidentiality and non-repudiation are both required. On the other hand, with the current development of rapid quantum computing, currently schemes based on traditional numerical assumptions (e.g., decisional Diffie-Hellman assumption) are more likely to be attacked by quantum computers. Therefore, lattice-based signcryption schemes have been extensively studied in recent years. However, most of them are either inefficient or secure-proved under the assumptions of random oracles. Although some of them are proved in the standard model, they are not practical in low-cost devices. Since the security is based on "Learning with Errors" (LWE) or "Short Integer Solution" problems, it will result in extremely large size of keys. In this paper, we propose an efficient NTRU-based signcryption scheme, which is inspired from Pion et al.'s key encapsulation mechanism. We provide rigorous security proofs for the confidentiality and unforgeability under NTRU-based assumptions in the standard model. Compared with other schemes, we conclude that our scheme is more efficient and secure.
Digital signatures are indispensable for security on the Internet, because they guarantee authenticity, integrity, and non-repudiation, of namely e-mails, software updates, and in the Transport Layer Security (TLS) protocol which is used for secure data transfer, for example. Most signature schemes that are currently in use such as the RSA signature scheme, are considered secure as long as the integer factorization problem or the discrete logarithm (DL) problem are computationally hard. At present, no algorithms have yet been found to solve these problems on conventional computers in polynomial time. However, in 1997, Shor published a polynomial-time algorithm that uses quantum computation to solve the integer factorization and the DL problem. In particular, this means that RSA signatures are considered broken as soon as large-scale quantum computers exist. Due to significant advances in the area of quantum computing, it is reasonable to assume that within 20 years, quantum computers that are able to break the RSA scheme, could exist. In order to maintain authenticity, integrity, and non-repudiation of data, cryptographic schemes that cannot be broken by quantum attacks are required. In addition, these so-called post-quantum secure schemes should be sufficiently efficient to be suitable for all established applications. Furthermore, solutions enabling a timely and secure transition from classical to post-quantum schemes are needed. This thesis contributes to the above-mentioned transition. In this thesis, we present the two lattice-based digital signature schemes TESLA and qTESLA, whereby lattice-based cryptography is one of five approaches to construct post-quantum secure schemes. Furthermore, we prove that our signature schemes are secure as long as the so-called Learning With Errors (LWE) problem is computationally hard to solve. It is presumed that even quantum computers cannot solve the LWE problem in polynomial time. The security of our schemes is proven using security reductions. Since our reductions are tight and explicit, efficient instantiations are possible that provably guarantee a selected security level, as long as the corresponding LWE instance provides a certain hardness level. Since both our reductions (as proven in the quantum random oracle model) and instantiations, take into account quantum attackers, TESLA and qTESLA are considered post-quantum secure. Concurrently, the run-times for generating and verifying signatures of qTESLA are similar (or faster) than those of the RSA scheme. However, key and signature sizes of RSA are smaller than those of qTESLA. In order to protect both the theoretical signature schemes and their implementations against attacks, we analyze possible vulnerabilities against implementation attacks. In particular, cache-side-channel attacks resulting from observing the cache behavior and fault attacks, which recover secret information by actively disrupting the execution of an algorithm are focused. We present effective countermeasures for each implementation attack we found. Our analyses and countermeasures also influence the design and implementation of qTESLA. Although our schemes are considered (post-quantum) secure according to state-of-the-art LWE attacks, cryptanalysis of lattice-based schemes is still a relatively new field of research in comparison to RSA schemes. Hence, there is a lack of confidence in the concrete instantiations and their promised security levels. However, due to developments within the field of quantum computers, a transition to post-quantum secure solutions seems to be more urgently required than ever. To solve this dilemma, we present an approach to combine two schemes, e.g., qTESLA and the RSA signature scheme, so that the combination is secure as long as one of the two combined schemes is secure. We present several of such combiners to construct hybrid signature schemes and hybrid key encapsulation mechanisms to ensure both authenticity and confidentiality in our Public-Key Infrastructure (PKI). Lastly, we also demonstrate how to apply the resulting hybrid schemes in standards such as X.509 or TLS. To summarize, this work presents post-quantum secure candidates which can, using our hybrid schemes, add post-quantum security to the current classical security in our PKI.
It is also worth noting that the implementation of quantum computing has been a big threat to the classical cryptographic algorithms that are popular in secure networked systems. PostQuantum Cryptography (PQC) has come to play as one of the viable answers to this issue because it has the capacity to resist quantum-enabled attacks. In this paper, the author offers a detailed performance analysis of post-quantum cryptographic algorithms, lattice-based encryption which is based on the Learning with Errors (LWE) principle, and hashbased digital signatures which is based on SPHINCS+. An experimental environment was created that is controlled by using specific performance measures, such as time of key generation, the latency of encryption and decryption, amount of memory, and the size of keys and ciphertext. To determine the suitability of PQC in guaranteeing confidentiality, integrity, and authenticity over insecure channels, secure network communication was emulated. Through experimental findings, it has been shown that the lattice-based generation of keys has greater overhead in terms of computation and memory, but the encryption, decryption and signature processes have feasible limits. The results validate the practicability of the post-quantum cryptography mechanisms implementation in the practical secure network systems and the trade-off between the increased quantum resistance and the resource consumption.
The rapid expansion of the Internet of Things (IoT) has led to an unprecedented scale of data exchange across heterogeneous and resource-constrained devices. Ensuring confidentiality and secure key management in such environments is challenging. Traditional public-key infrastructures require heavy certificate-handling overhead. Identity-Based Encryption (IBE) offers a lightweight alternative by deriving public keys directly from device identities, making it attractive for IoT deployments. However, IoT devices are highly vulnerable to side-channel and key-extraction attacks, motivating the need for Forward-Secure IBE(FS-IBE), where the compromise of a current secret key does not threaten past communications. Existing FS-IBE constructions based on classical hardness assumptions are not secure in the era of post-quantum, while the lattice-based (LWE-based) forward-secure scheme suffer from large key and ciphertext sizes, limiting their suitability for constrained IoT systems. Here, we propose a new lattice-based fs-IBE scheme in the ring setting, relying on the RLWE assumption to achieve post-quantum security and significant efficiency gains. Our design uses trapdoor delegation with a minimal-cover mechanism over a binary tree. It results in compact public parameters and efficient per-epoch key updates. Compared to prior LWE-based constructions, our scheme reduces public key, secret key, and ciphertext sizes, and thus, making it better suited for practical IoT environments.
Post-quantum cryptography (PQC) aims to develop cryptographic protocols resistant to attacks by quantum computers, which threaten classical schemes based on integer factorization and discrete logarithm problems. Among various approaches, lattice-based cryptography has emerged as one of the most promising candidates for PQC. Within this domain, ring theory plays a foundational role by providing the algebraic structures—specifically polynomial rings modulo cyclotomic polynomials—used to define hard problems like Ring Learning With Errors (Ring-LWE). These problems underpin efficient and secure cryptographic primitives such as key exchange, encryption, digital signatures, and homomorphic encryption. This paper explores the theoretical background of ring theory relevant to PQC and discusses how it enables the construction of cryptosystems with strong security assumptions and practical efficiency. We also analyze specific schemes that utilize ring-based lattices, including New Hope, NTRUEncrypt, and Dilithium, highlighting the advantages of ring structures in reducing key sizes and improving computational speed. Furthermore, we review the implementation challenges and potential future directions for integrating ring theory into next-generation cryptographic protocols suitable for a post-quantum world.