Witness Encryption (WE) enables encryption under computational problems where decryption requires knowledge of a valid witness to a nondeterministic polynomial-time (NP) statement. While theoretical constructions exist for all NP languages using complex assumptions like multilinear maps, practical schemes remain limited to specialized relations. We present the first extractable Witness Key Encapsulation Mechanism (WKEM) for Quadratic Arithmetic Programs (QAPs), the mathematical foundation underlying modern zkSNARKs including Groth16. Our construction transforms Groth16’s verification equations into an encryption mechanism, enabling practical witness encryption for rich algebraic relations expressible as arithmetic circuits. We prove extractability in the Algebraic Group Model combined with the Random Oracle Model, providing a clean reduction to Groth16’s computational knowledge soundness without requiring novel assumptions. Our WKEM composes generically with symmetric encryption to yield a complete extractable WE scheme for QAP relations. We validate our construction through a complete implementation with practical performance: circuits with 162–150K constraints achieve encryption/decryption in ∼20 ms to ∼1.7 s. Our approach bridges the gap between WE theory and practice by building on the mature zkSNARK ecosystem while maintaining strong extractability guarantees.

The Fiat-Shamir with Aborts (FSwA) paradigm is a well-established approach to construct lattice-based signatures, leading to many efficient and practical schemes. One of popular implementations is Dilithium, which has been selected as the standardization in the post-quantum project by NIST. An important question now is whether the signature schemes following the FSwA framework allow for additional features, such as aggregation of different signatures. To our knowledge, only a few schemes have been proposed, most of them lack a sound security proof or suffer from inefficiency, highlighting the need for further research. Motivated by this circumstance, we propose a FSwA-based non-interactive aggregate signature scheme which not only achieves the aggregate signature smaller than the trivial concatenation of all individual signatures, but also gives a provable security proof. In addition, we review the state of the art of the FSwA-based aggregate signatures, including the schemes presented by Boudgoust and Roux-Langlois in the Computer Journal (2023) and by Tomita and Shikata (IACR eprint 2023/471), and observe certain issues in their constructions which inspire our design.

In this study, we revisit the cryptosystem termed public-key encryption with filtered equality test (PKEFET), originally devised by Huang et al. (J. Comput. Syst. Sci. 2017) and subsequently refined by Chen et al. (Des. Codes Cryptogr. 2021). This notion allows users to delegate the equality test functionality of ciphertexts to a tester, but only for ciphertexts associated with a selected message set. More specifically, consider two ciphertexts related to plaintexts m and m ', along with their respective tokens related to two plaintext sets m and m '. Assuming m is an element of m and m ' is an element of m ' hold simultaneously, then any tester has the ability to determine if the ciphertexts are associated with an identical plaintext (i.e., m = m '). With this functionality, PKEFET is valuable in applications such as encrypted data search and spam filtering. However, there exist several challenges in the current PKEFET schemes, such as: (i) security is limited to indistinguishability against "non-adaptive" chosen-ciphertext attacks (CCA1) and (ii) the computational and storage complexities scale linearly with the maximum number of plaintexts that a token can authenticate. To address these challenges, by employing public-key encryption and key-policy attribute-based encryption (KPABE) supporting OR-gate policies as the foundational building blocks, we propose a generic construction of PKEFET. In particular, we show that the required KPABE can be obtained from identity-based encryption. We demonstrate that the proposed construction satisfies one-wayness and indistinguishability under strong filtered equality test against adaptive chosen-ciphertext attacks (CCA2). Moreover, the resulting scheme has significant computational and storage complexity advantages compared to existing PKEFET schemes.

Receiver selective opening (RSO) security considers the security of encryption schemes under the scenario of a single sender and multiple receivers, where an adversary is allowed to adaptively corrupt some receivers’ secret keys. RSO security has been proven to be more secure than indistinguishability-based security notions. A lot of research has focused on RSO security in terms of public-key encryption and identity-based encryption (IBE); however, hierarchical IBE (HIBE), which is a generalization of IBE, is still lacking in the study, and how to obtain such a construction remains an open problem. To address this gap, we initiate a study of RSO security on HIBE in this work. Precisely, we first formalize the definition of simulation-based RSO against identity-chosen-plaintext/ciphertext attacks in the k-challenge setting (SIM-ID-RSO _k -CPA/CCA) for HIBE. We then present generic SIM-ID-RSO _k -CCA secure HIBE constructions by introducing the double secret key paradigm. Specifically, we show that a SIM-ID-RSO _k -CCA secure HIBE scheme can be obtained from an IND-ID-CPA secure HIBE scheme as well as a one-time signature scheme that satisfies strong unforgeability. Through our general construction, we can derive various concrete schemes based on different hard assumptions (e.g., lattice-based and pairing-based SIM-ID-RSO _k -CCA secure HIBE schemes) according to usage requirements.

Accumulators enable succinct membership proofs and are critical for credential revocation and other verifiable services. In the post-quantum setting, hash-based accumulators remain transparent but incur log n overhead, while RSA alternatives achieve constant costs but are not quantum-safe. Lattice-based constructions from the PASS lineage provide constant-size proofs with transparent setup, yet existing candidates either require trapdoors or yield large witnesses. We present COMPASS, an improved lattice-based accumulator that is trapdoor-free, quantitatively analyzed, and fully implemented. Our proof-of-concept demonstrates constant-size witnesses as small as 4.3 KiB and verification times as short as 3.6 ms at PASS _G -style parameter points, maintaining the 128-bit BKZ-GSA security margin. Compared with our re-implementation of Maeno et al., COMPASS achieves up to 52

The Internet of Things faces significant security challenges, particularly in device authentication. Traditional methods of PUF-based authentication protocols do not fully address IoT's unique security needs and resource constraints. Existing solutions like Identity-Based Encryption with Physically Unclonable Functions enhance security but still struggle with protecting data during transmission. We show a new protocol that leverages PUFs for device authentication by utilizing Paillier homomorphic encryption or the plaintext equality test to enhance security. Our approach involves encrypting both the challenge-response pairs (CRPs) using Paillier homomorphic encryption scheme or ElGamal encryption for plaintext equality testing scheme. The verifier does not need access to the plaintext CRPs to ensure that sensitive data remain encrypted at all times and our approach reduces the computational load on IoT devices. The encryption ensures that neither the challenge nor the response can be deciphered by potential adversaries who obtain them during the transmission. The homomorphic property of the Paillier scheme or plaintext equality testing scheme allows a verifier to verify device authenticity without decrypting the CRPs, preserving privacy and reducing the computational load on IoT devices. Such an approach to encrypting both elements of the CRP provides resistance against CRP disclosure, machine learning attacks, and impersonation attacks. We validate the scheme through security analysis against various attacks and evaluate its performance by analyzing the computational overhead and the communication overhead. Comparison of average computational and communication time demonstrates Paillier scheme achieves approximately 99% reduction while the plaintext equality test achieves approximately 94% reduction between them.

Quantum dataset preprocessing for amplitude embedding is understudied despite its importance for achieving good generalization in quantum machine learning models. Amplitude embedding, known for its compression capabilities, has garnered attention in recent research. Combined with the Variational Quantum Classifier, they form a potential combination for high performance in quantum machine learning, outperforming many classical models. However, the full normalization of amplitude embedding has fundamental issues, such as inconvertibility for specific values and irrational amplitude distribution due to normalization. To overcome these challenges, we propose a novel and straightforward dataset preprocessing solution using guardian parity designed for amplitude embedding. This method ensures the normalized dataset remains recoverable to its original MinMax scaled values, simultaneously enhancing dataset quality and improving accuracy when employed in quantum machine learning models. Experimental results show that the proposed parity-based amplitude embedding significantly impacts the accuracy of machine learning models compared to the original amplitude embedding method.

Ensuring authorized access control in the IoT is vital for privacy and safety protection. Our study presents the novel IHIBE framework, which combines IOTA (a distributed ledger technology) with hierarchical identity-based encryption (HIBE), thereby enhancing both IoT security and scalability. This approach secures access tokens and policies while reducing the computational demand on data owners. Our empirical findings reveal a significant performance gap, with access rights delegation on the Raspberry Pi 4 exceeding those on AWS by over 250%. Moreover, our analysis uncovers optimal identity policy depths: up to 640 identities on AWS and 640 on the Raspberry Pi 4 for systems with higher tolerable delays, and 320 identities on AWS versus 160 on the Raspberry Pi 4 for systems with lower tolerable delays. The system shows practical viability, exhibiting insignificant operational time differences compared to Zhang et al.’s schemes, particularly in access rights verification processes, with a minimal difference of 33.35%. Our extensive security assessment, encompassing scenarios like encrypted token theft and compromise of authority, affirms the efficacy of our challenge-response and last-word challenge (LWC) mechanisms. This study underscores the importance of platform choice in IoT system architectures and provides insights for deploying efficient, secure, and scalable IoT environments.

Cloud-based data sharing systems (DSS) have become prevalent due to their ample storage and convenient access control. To protect sensitive data privacy in DSS, anonymous identity-based encryption (IBE) is a promising approach, enabling encryption using a recipient’s identity as a public key, while preventing identity and data leaks out of ciphertexts. As complete anonymity risks abuse and illegal usage, Blazy et al. introduced the notion called anonymous IBE with traceable identities (AIBET) at ARES’19, allowing users with tracing keys to identify recipients from ciphertexts. Unfortunately, existing AIBET schemes lack tracing key delegation and only consider security in weaker models (i.e., selective-identity attacks and chosen-plaintext attacks), posing risks of inconvenience and user privacy leaks. In this paper, we introduce a novel notion called anonymous hierarchical identity-based encryption with delegated traceability (AHIBEDT) for DSS. We formalize its syntax and define security notions in stronger models (i.e., adaptive-identity attacks and chosen-ciphertext attacks). In addition, we demonstrate that a concrete AHIBEDT scheme can be simply obtained from a hierarchical IBE scheme and a one-time signature scheme. The comparison results indicate that, despite a substantial increase in communication and computational costs, our approach achieves better security and functionality.

With the widespread adoption and increasing application of blockchain technology, cryptocurrency wallets used in Bitcoin and Ethereum play a crucial role in facilitating decentralized asset management and secure transactions. However, wallet security relies heavily on private keys, with insufficient attention to the risks of theft and exposure. To address this issue, Chaum et al. (ACNS’21) proposed a “proof of ownership” method using a “backup key” to prove ownership of private keys even when exposed. However, their interactive proof approach is inefficient in large-scale systems and vulnerable to side-channel attacks due to the long key generation time. Other related schemes also suffer from low efficiency and complex key management, increasing the difficulty of securely storing backup keys. In this paper, we present an efficient, non-interactive proof generation approach for ownership of secret keys using a single backup key. Our approach leverages non-interactive zero-knowledge proofs and symmetric encryption, allowing users to generate multiple proofs with one fixed backup key, simplifying key management. Additionally, our scheme resists quantum attacks and provides a fallback signature. Our new scheme can be proved to capture unforgeability under the computational indistinguishability from the Uniformly Random Distribution property of a proper hash function and soundness in the quantum random oracle model. Experimental results indicate that our approach achieves a short key generation time and enables an efficient proof generation scheme in large-scale decentralized systems. Compared with state-of-the-art schemes, our approach is applicable to a broader range of scenarios due to its non-interactive nature, short key generation time, high efficiency, and simplified key management system.

Designing a quantum data compression circuit with reasonable error using autoencoders can be time-consuming. Previous studies have explored qubit compression using specially designed circuits or autoencoders, with some attempts to apply it to small 16-bit black-and-white images using four qubits. However, analysis regarding the errors using general data is not discussed enough. This paper proposes a practical technique to optimize quantum compression for general data comprising hundreds of thousands of classical data points. We introduce Quantum State Error to investigate the potential for improving accuracy through qubit selection using degree reduction in quantum compression. By doing so, imperfect quantum autoencoder circuits may exhibit enhanced performance, offering improved lossy compression capabilities. Our experiments show promising results, where certain kind of circuits responds well to degree reduction by a factor of 3/4, reducing the number of faulty qubits up to 11.44%.

Existing detection techniques for Linux fileless mal-ware are not resistant to tampering with commands and files. In this paper, we propose three evasion methods using extended Berkley Packet Filter (eBPF) against the detection methods for Linux fileless malware. We implement the evasion techniques and demonstrate their feasibility. Additionally, we discuss mitigations against the evasions to improve the robustness of the existing detection methods.

The emergence of cloud computing enables users to upload data to remote clouds and compute them. This drastically reduces computing and storage costs for users. Considering secure computing for multilevel users in enterprises, the notion of hierarchical identity-based inner product functional encryption (HIB-IPFE) is proposed. In this cryptosystem, a sender can encrypt a vector x→ into a ciphertext with a hierarchical identity, while a receiver who possesses a secret key corresponding to the same hierarchical identity and a vector y→ can decrypt the ciphertext and obtain the inner product x→,y→. However, HIB-IPFE is not sufficient to capture flexible data sharing and forward security. In this study, we present a notion of hierarchical identity-based puncturable HIBP-IPFE. Furthermore, we present a formal definition and security model of HIBP-IPFE to guarantee data confidentiality and receiver anonymity. Compared with HIB-IPFE, our proposed scheme enables users to puncture keys on specific tags ensuring that the punctured keys cannot be used to decrypt the ciphertexts associated with those tags. The proposed scheme is provably secure under d-DBDHE assumption in the standard model. The experimental results indicate that our scheme is more practical in cloud computing, with superior functionality.

Due to the widespread use of distributed data mining techniques in a variety of areas, the issue of protecting the privacy of sensitive data has received increasing attention in recent years. Privacy-preserving distributed data mining (PPDDM) focuses on decentralized data analysis without the disclosure of sensitive information from data owner. However, the previous PPDDM mostly works on a limited amount of labeled data. In contrast to the real world, unlabeled data is abundance and labeled data is scarce. The objectives of this paper are to study and to analyze privacy-preserving properties of semi-supervised learning (SSL) algorithm with the combination of labeled and unlabeled data, where data is distributed among multiple data owners. In this paper we propose a Privacy-preserving Distributed Data Mining (PPDDM) method by designing a reliable application of secure MPC to semi-supervised tri-training algorithms. We simulate the original tri-training algorithm and tri-training algorithm with secure MPC using a different types of classifiers and datasets. The simulation results show that tri-training in secure MPC has almost same accuracy compared to original tri-training algorithm. We also compare execution time in addition to performance evaluation of tri-training in secure and the original tri-training algorithms.

Public key encryption with keyword search (PEKS), which was introduced by Boneh et al. at EUROCRYPT’ 04, is a breakthrough approach to searching encrypted data under a public key setting. In this cryptographic primitive, senders can generate searchable ciphertexts for specific keywords to be retrieved from a given document; receivers can generate corresponding trapdoors for search by using their private keys. Recently, Jiang et al. (ACISP’ 16) proposed an improved PEKS scheme called public key encryption with authorized keyword search (PEAKS); this scheme enables authorized users to generate trapdoors for specific sets of keywords even if these users do not have access to the private key. Unfortunately, authorized users cannot delegate this power to other unauthorized users because the authorization in PEAKS is insufficiently flexible; therefore, this scheme is not suitable for enterprise scenarios in general. In this work, we introduce a novel cryptographic primitive called public key encryption with hierarchical authorized keyword search (PEHAKS) to solve this problem. In contrast to PEAKS, the proposed primitive enables authorized users to further hierarchically delegate their power of generating trapdoors to unauthorized users. We formally define the system model of PEHAKS under a multikeyword setting, and the security requirements are designed to withstand attacks in a real scenario. Furthermore, we propose a provably secure scheme using the technique of dual pairing vector spaces and demonstrate that the scheme is secure under the hardness of the n-extended decisional Diffie–Hellman assumption. Therefore, the proposed scheme is secure and can be applied in scenarios that require hierarchical authorization. To the best of the authors’ knowledge, no PEKS variant schemes with this property have been previously designed.

Fuzzy signatures (FS) are a kind of signature scheme that employs a noisy string (e.g., biometric data) as the secret key without requiring the user-specific auxiliary data. As the quantum computing era approaches, some research has been dedicated to developing quantum-resistant FS schemes, which can be classified into fuzzy extractor (FE) approach and linear sketch (LS) approach. However, the existing schemes utilizing FEs to obtain (variants of) fuzzy signatures require to produce the user-specific auxiliary information known as helper data to retrieve secret keys, leading to an additional computational cost. In light of the circumstance, we seek to construct a fuzzy signature scheme by employing a linear sketch, since this approach does not require the user-specific auxiliary data to derive secret keys. We modify the linear sketch which is an essential ingredient of the most practical fuzzy signature proposed by Katsumata et al. (CCS' 21). Then we combine it with Lyubashevsky's lattice-based signature scheme (EUROCRYPT' 12) to construct our lattice-based fuzzy signature scheme. Moreover, to further demonstrate the security of our proposed scheme, we provide a rigorous security proof in the random oracle model. Finally, the comparison indicates that our proposed FS scheme not only avoids the use of FE but also shows a promising tendency in efficiency among the existing quantum-resistant FS schemes.

Internet Engineering Task Force (IETF) issued Secure Zero Touch Provisioning (SZTP) as a provisioning technique for networking devices without human intervention. SZTP standardizes the provisioning workflow from device enrollment to bootstrapping process. Unfortunately, implementing a single trust model of public key infrastructure scheme in zero-touch device provisioning is vulnerable to impersonation attacks using bogus certificates. This paper proposes a robust protocol for the bootstrapping process of edge devices by integrating the Attack Resilient Public Key Infrastructure (ARPKI) scheme with SZTP. As a transparent and accountable public key infrastructure, ARPKI can prevent the miss-issuance of a certificate. ARPKI offers strong security as certificate management for SZTP. We adopt the security properties of ARPKI to construct an accountable bootstrapping scheme of a zero-touch provisioned edge device against threats, e.g., impersonation, incurred by insiders compromised by adversaries. The edge device and bootstrap server can confidently build mutual authentication using the TLS 1.3 full handshake protocol together with the ARPKI-based certificates built upon a trusted public certificate log, which provides the accountability of the certificate. We analyze our scheme’s security properties by performing formal and informal analyses. We show that the combination of ARPKI and SZTP can detect malicious entities and mitigate misbehaving activities. Our provisioning scheme provides accountable bootstrapping for edge devices in a zero-touch fashion with integrity and confidentiality of bootstrapping data.

Vehicle to everything (V2X) technology allows the broader development of driving safety, efficiency, and comfort. Because the vehicles can quickly send and receive frequent messages from other vehicles and nearby devices, e.g., cooperative awareness message applications on the intelligent transport system (ITS), V2X requires a good security and privacy protection system to make the messages reliable for the ITS requirements. The existing standards developed in the US and Europe use many short valid period pseudonym certificates to meet the security and privacy requirements. However, this method has difficulty ensuring that revoked pseudonym certificates are treated as revoked by any vehicles because distributing revocation information on a wireless vehicular network with intermittent and rapidly changing topology is demanding. A promising approach to solving this problem is the periodic activation of released pseudonym certificates. Initially, it releases all required pseudonym certificates for a certain period to the vehicle, and pseudonym certificates can be used only after receiving an activation code. Such activation-code-based schemes have a common problem in the inefficient use of network resources between the road-side unit (RSU) and vehicles. This paper proposes an efficient and privacy-preserving activation code distribution strategy solving the problem. By adopting the unicast distribution model of modified activation code for pseudonym certificate (ACPC), our scheme can obtain benefits of efficient activation code distribution. The proposed scheme provides small communication resource usage in the V2X network with various channel options for delivering activation codes in a privacy preserved manner.

Active learning is a technique for maximizing performance of machine learning with minimal labeling effort and letting the machine automatically and adaptively select the most informative data for labeling. Since the labels on records may contain sensitive information, privacy-preserving mechanisms should be integrated into active learning. We propose a privacy-preservation scheme for active learning using homomorphic encryption-based federated learning. Federated learning provides distributed computation from multiple clients, and homomorphic encryption enhances the privacy preservation of user data with a strong security level. The experimental result shows that the proposed homomorphic encryption-based federated learning scheme can preserve privacy in active learning while maintaining model accuracy. Furthermore, we also provide a Deep Leakage Gradient comparison. The proposed scheme has no gradient leakage compared to the related schemes that have more than 74% gradient leakage.

Due to the rapid deployment of zero-touch provisioned devices, the Internet of Things (IoT) has become a complex network. The increased number of connected devices improves network accessibility, but it also results in an expanded attack surface. The security of the device's lifecycle needs careful attention. We discuss a lifecycle of zero-touch provisioned devices and its security in the IoT networks. The adoption of zero-touch provisioned devices stimulates the evolution of new types of security attacks. Based on the typical security properties, we consider the best practice to ensure the security of a zero-touch provisioned device's lifecycle. Ensuring identification management is one of the crucial aspects of achieving security properties. It deals with the identity construction of each device, authenticating the authorized devices, and detecting malicious activities. We confirm that our security design of zero-touch provisioned device lifecycle can satisfy the fundamental security properties.