Internet of Things (IoT)-based devices, especially those used for home automation, consist of their own sensors and generate many logs during a process. Enterprises producing IoT devices convert these log data into more useful data through secondary processing; thus, they require data from the device users. Recently, a platform for data sharing has been developed because the demand for IoT data increases. Several IoT data marketplaces are based on peer-to-peer (P2P) networks, and in this type of marketplace, it is difficult for an enterprise to trust a data owner or the data they want to trade. Therefore, in this study, we propose a review system that can confirm the reputation of a data owner or the data traded in the P2P data marketplace. The traditional server-client review systems have many drawbacks, such as security vulnerability or server administrator’s malicious behavior. However, the review system developed in this study is based on Ethereum smart contracts; thus, this system is running on the P2P network and is more flexible for the network problem. Moreover, the integrity and immutability of the registered reviews are assured because of the blockchain public ledger. In addition, a certain amount of gas is essential for all functions to be processed by Ethereum transactions. Accordingly, we tested and analyzed the performance of our proposed model in terms of gas required.

At present, there is a considerable increase in the amount of data stored in storage services, along with dramatic evolution of networking techniques. In storage services with huge data, the storage servers may want to reduce the volume of stored data, and the clients may want to monitor the integrity of their data with a low cost, since the cost of the functions related to data storage increase in proportion to the size of the data. To achieve these goals, secure deduplication and integrity auditing delegation techniques have been studied, which can reduce the volume of data stored in storage by eliminating duplicated copies and permit clients to efficiently verify the integrity of stored files by delegating costly operations to a trusted party, respectively. So far many studies have been conducted on each topic, separately, whereas relatively few combined schemes, which support the two functions simultaneously, have been researched. In this paper, we design a combined technique, which performs both secure deduplication of encrypted data and public integrity auditing of data. To support the two functions, the proposed scheme performs challenge-response protocols using the BLS signature-based homomorphic linear authenticator. We utilize a third party auditor for performing public audit, in order to help low-powered clients. The proposed scheme satisfies all the fundamental security requirements. We also propose two variances that provide higher security and better performance.

Currently, “connected cars” are being actively designed over smart cars and autonomous cars, to establish a two-way communication network between the vehicle and all infrastructure. Additionally, because vehicle black boxes are becoming more common, specific processes for secure and efficient data sharing and transaction via vehicle networks must be developed. In this paper, we propose a Blockchain-based vehicle data marketplace platform model, along with a data sharing scheme, using Blockchain-based data-owner-based attribute-based encryption (DO-ABE). The proposed model achieves the basic requirements such as data confidentiality, integrity, and privacy. The proposed system securely and effectively handles large-capacity and privacy-sensitive black box video data by storing the metadata on Blockchain (on-chain) and encrypted raw data on off-chain (external) storage, and adopting consortium Blockchain. Furthermore, the data owners of the proposed model can control their own data by applying the Blockchain-based DO-ABE and owner-defined access control lists.

The continuous development of the mobile computing environment has led to the emergence of fintech to enable convenient financial transactions in this environment. Previously proposed financial identity services mostly adopted centralized servers that are prone to single-point-of-failure problems and performance bottlenecks. Blockchain-based self-sovereign identity (SSI), which emerged to address this problem, is a technology that solves centralized problems and allows decentralized identification. However, the verifiable credential (VC), a unit of SSI data transactions, guarantees unlimited right to erasure for self-sovereignty. This does not suit the specificity of the financial transaction network, which requires the restriction of the right to erasure for credit evaluation. This paper proposes a model for VC generation and revocation verification for credit scoring data. The proposed model includes double zero knowledge - succinct non-interactive argument of knowledge (zk-SNARK) proof in the VC generation process between the holder and the issuer. In addition, cross-revocation verification takes place between the holder and the verifier. As a result, the proposed model builds a trust platform among the holder, issuer, and verifier while maintaining the decentralized SSI attributes and focusing on the VC life cycle. The model also improves the way in which credit evaluation data are processed as VCs by granting opt-in and the special right to erasure.

These days, data is regarded as a valuable asset in the era of the data economy, which demands a trading platform for buying and selling data. However, online data trading poses challenges in terms of security and fairness because the seller and the buyer may not fully trust each other. Therefore, in this paper, a blockchain-based secure and fair data trading system is proposed by taking advantage of the smart contract and matchmaking encryption. The proposed system enables bilateral authorization, where data trading between a seller and a buyer is accomplished only if their policies, required by each other, are satisfied simultaneously. This can be achieved by exploiting the security features of the matchmaking encryption. To guarantee non-repudiation and fairness between trading parties, the proposed system leverages a smart contract to ensure that the parties honestly carry out the data trading protocol. However, the smart contract in the proposed system does not include complex cryptographic operations for the efficiency of on-chain processes. Instead, these operations are carried out by off-chain parties and their results are used as input for the on-chain procedure. The system also uses an arbitration protocol to resolve disputes based on the trading proof recorded on the blockchain. The performance of the protocol is evaluated in terms of off-chain computation overhead and on-chain gas consumption. The results of the experiments demonstrate that the proposed protocols can enable the implementation of a cost-effective data trading system.

Since deduplication inevitably implies data sharing, control over access permissions in an encrypted deduplication storage is more important than a traditional encrypted storage. Therefore, in terms of flexibility, data deduplication should be combined with data access control techniques. In this paper, we propose an authorized deduplication scheme using CP-ABE to solve this problem. The proposed scheme provides client-side deduplication while providing confidentiality through client-side encryption to prevent exposure of users’ sensitive data on untrusted cloud servers. Also, unlike existing convergent encryption schemes, it provides authorized convergent encryption by using CP-ABE to allow only authorized users to access critical data. The proposed authorized deduplication scheme provides an adequate trade-off between storage space efficiency and security in cloud environment and is very suitable for the hybrid cloud model considering both the data security and the storage efficiency in a business environment.