Proof of Stake (PoS) blockchain systems require weighted threshold signatures where participants' voting powers reflect their stakes. As stakes change dynamically through deposits and withdrawals, efficient weight and threshold adjustments are essential for maintaining system security and availability without downtime. However, existing approaches face critical limitations: (1) virtualization-based schemes require$O(w)$operations (signatures) per participant with weight$w$; (2) dynamic threshold / paricipants schemes do not support weighted participants; (3) schemes with both properties require trusted dealers or$O(n^{2})$re-setup, causing temporary unavailability. This paper introduces Active Weighted Signature (AWS), enabling dynamic adjustments without trusted dealers or re-setup. We propose Generalized Lagrange Interpolation (GLI), encoding weights as polynomial derivatives rather than virtualized participants, and instantiate AWS through$ {\sf ADAPT}$by applying GLI to the Schnorr-based threshold signature${\sf FROST}$. Our implementation shows that$ {\sf ADAPT}$achieves comparable efficiency to${\sf FROST}$for key generation, while weight and threshold adjustments complete in 4.1-22.3% of re-setup time. For uneven weight distributions,$ {\sf ADAPT}$achieves sub-linear scaling: 49× weight difference requires only 3.29× computation versus 49× in virtualization.

As blockchain technology is adopted in innovative fields like the Internet of Things, software-defined IoT, QoS-aware software-defined IoT, software-defined Internet of Multimedia Things, and streaming in software-defined Internet of Vehicles, it faces scalability challenges, including rapidly increasing transaction throughput, confirmation delays, and rising fees. An emerging technique, sharding is a solution to scale the blockchain by processing transactions in parallel. The sharding splits the main network into subnetworks, called shards, to process transactions. Sharding techniques for blockchain scalability face challenges in minimizing cross-shard transactions and avoiding unnecessary or delayed account relocations due to random shard assignments. In this paper, we introduce a greedy account relocation algorithm to reduce the number of cross-shard transactions. In our algorithm, the accounts are first sorted according to the number of cross-shard transactions they are responsible for, and then the accounts are reassigned to a target shard if the relocation satisfies given constraints. Our algorithm can reduce the cross-shard transactions more than 30% compared to the existing relocation algorithms, still keeping load balancing between shards.

A multiproxy signature scheme constructs a legitimate signature by a proxy group when an original signer is absent. In this article, we newly propose an efficient and provably secure ID-based multiproxy signature (IBMPS) from bilinear pairings based on a random proxy signing key. We observe that a proxy signing key from a proxy key generation (PKG) makes IBMPS much more efficient and secure than directly using a private key for a multiproxy signature. We show formal security results under the computational Diffie–Hellman assumption with PKG queries in the random oracle. Our scheme not only preserves provable security but also achieves the least computation cost in the signing and verification phase than other IBMPS schemes. To show its applicability in Internet of Drones (IoD), which usually demands greater efficiency due to the limited resources while the drones are in flight, we also present a practical on/offline IBMPS for an IoD setting. Our on/offline IBMPS scheme just requires one point scalar addition for generating a proxy signature in terms of each proxy signer. Considering that our IBMPS schemes can be practical in urgent situations, e.g., surveillance and rescue operations, we show our implementation of IBMPS schemes on a Raspberry Pi drone platform along with the relevant schemes. We demonstrate that our schemes are considerably more efficient than others with respect to computation time and energy consumption by the number of proxy signers.

To prevent the leakage of original biometric information of a user, it may be transformed into a cancelable form. A cancelable biometric transformation should satisfy four requirements: unlinkability, revocability, noninvertibility, and performance. In 2014, Moujahdi et al. proposed a new cancelable fingerprint transformation called fingerprint shell, which was also later discussed by Ali et al. In this paper, we show that all of the shell fingerprint schemes presented by Moujahdi et al. and Ali et al. do not satisfy the condition of unlinkability.

When biometric authentication is performed on On-Body Wearable Wireless Networks, a cancelable template is useful to protect biometric information. A cancelable template generation method converts the original biometric information into irreversibly transformed information to protect the original biometric information. If a cancelable template is damaged or leaked, it can be replaced with another cancelable template. In 2017, Dwivedi et al. proposed a novel cancelable iris template generation scheme based on the randomized look-up table mapping. So far their scheme is the most accurate scheme with respect to EER compared to the previous cancelable iris template generation schemes. However, their scheme is not alignment-free and so is not efficient enough for wearable sensors. In the paper, we first suggest how to improve the accuracy of the Dwivedi et al.’s scheme using the partial sort technique. Our experiment result shows that our suggested scheme is more accurate than the Dwivedi et al.’s scheme under almost all parameter settings. More concretely, our scheme achieves EER 0.09%, whereas the Dwivedi et al.’s scheme achieves EER 0.43% in the best parameter settings for the CASIA-V3-Interval iris database. We also suggest how to improve the efficiency of the Dwivedi et al.’s scheme. Our second scheme is alignment-free by processing IrisCode column-wise, whereas the Dwivedi et al.’s scheme handles IrisCode row-wise. Our experiment shows that our second scheme is 15 times faster than the Dwivedi et al.’s scheme, so our scheme is efficient enough for wearable sensors. Though our second scheme has very high EER under some parameter settings, our second scheme achieves EER 0.53% in the best parameter settings for the CASIA-V3-Interval iris database.

Biometric authentication in wearable devices is different from the common biometric authentication systems. First of all, sensitive information such as fingerprint and iris of a user is stored in a wearable device owned by the user rather than being stored in a remote database. Wearable devices are portable, and there is a risk that the devices might be lost or stolen. In addition, the quality of the extracted image from the wearable devices is lower than that of the common biometric acquisition sensor. In the paper, we propose a novel cancelable fingerprint template which is irreversible to the original biometrics and has excellent accuracy even in low quality images.

To provide the integrity of outsourced data in the cloud storage services, many public auditing schemes which allow a user to check the integrity of the outsourced data have been proposed. Since most of the schemes are constructed on Public Key Infrastructure (PKI), they suffer from several concerns like management of certificates. To resolve the problems,certificatelesspublic auditing schemes also have been studied in recent years. In this paper, we propose a certificateless public auditing scheme which has theconstant-time verification algorithm. Therefore, our scheme is more efficient than previous certificateless public auditing schemes. To prove the security of our certificateless public auditing scheme, we first define three formal security models and prove the security of our scheme under the three security models.

Abstract In a strong designated verifier signature scheme, only the designated verifier can determine the identity of the signer; others cannot identify the signer or the verifier. To date, one strong designated verifier signature scheme from lattices has been proposed, only in the random oracle model. In this paper, we propose the first strong designated verifier signature scheme from lattices in the standard model. The proposed scheme satisfies the requirements of unforgeability, nontransferability, and privacy of the signer's identity. This scheme can be easily extended to an identity‐based strong designated verifier signature scheme and an (identity‐based) strong multi‐designated verifiers signature scheme. Copyright © 2017 John Wiley & Sons, Ltd.

Abstract In identity‐based signatures, the key generation center (KGC) always knows user private key, and thus, it can always impersonate the user. Certificateless signatures were introduced by Al‐Riyami and Paterson to solve this key escrow problem of identity‐based signatures in 2003. In certificateless signatures, the private key is determined by neither the user nor the KGC. In 2007, Huang et al. revisited the security models of certificateless signatures. They divided potential adversaries according to their attack power into normal, strong and super adversaries. On the other hand, Au et al. introduced a new attack called malicious‐but‐passive KGC attack in the same year. In the new attack, KGC that holds the master secret key is assumed malicious at the very beginning of the setup phase of the system. The previous schemes that can be proven secure against malicious‐but‐passive KGC attack provided only the security against strong adversaries. In this paper, we construct the first certificateless signature scheme that can be proven secure against malicious‐but‐passive KGC attack of super adversaries. Moreover, our scheme is still secure when the adversary is allowed to obtain valid signatures on the target identity and message. Our construction is based on the hard lattice problems in the random oracle model.Copyright © 2014 John Wiley & Sons, Ltd.

Abstract In 2012, D. Schr der and H. Schr der introduced verifiable data streaming (VDS) that enables a client to append, search, verify, and update the streamed data efficiently. After storing the data with a server, a client issues a query to receive a proof that the data of the client are still correctly stored. Anyone can check the validity of the proof publicly in VDS. However, the length of a secret of a client, the length of a proof, and the complexity of appending an element in the previous VDS schemes are O(logn), where n is the upper bound on the number of elements to be stored. In this paper, we suggest a more efficient VDS scheme. In our scheme, the length of a secret of a client is only O(1), and the length of a proof and the complexity of appending an element are O(logi), where i(≤n) is the index of an element. We also show that our scheme is secure under any collision‐resistant hash functions and unforgeable signature schemes without random oracles. Copyright © 2015 John Wiley & Sons, Ltd.

Hospitals have to use a large amount of medical data from individuals while protecting their privacy to execute medical data mining. It is important to find ‘rare’ cases among medical data of individuals in many healthcare applications. Therefore hospitals need privacy-preserving mining techniques to find rare cases among medical data of individuals. However, previous privacy-preserving data-mining techniques cannot be used to find rare cases. In this study, they suggest a privacy-preserving ‘range set union’ protocol that can be used to find rare cases in the private medical datasets of individuals.

We suggest a linkable ring signature scheme providing strong anonymity and weak linkability. We show that our linkable ring signature scheme can be used to construct a selectively linkable ring signature scheme, an efficient convertible (verifiable) ring signature scheme, and an efficient deductible ring signature scheme.