A verifiable and privacy-preserving cloud mining pool selection scheme in blockchain of things

Highlights

• We propose a verifiable way to judge whether cloud mining pools are honest. This method enables fast verification without being affected by the performance limitations of IoT devices, while also helping IoT devices to select high-performance cloud mining pools in BCoT.

• By implementing the additive homomorphic ElGamal cryptosystem, we not only achieve privacy protection in data transmission but also utilize a semi-honest cloud server to reduce the computational overhead of resource-constrained IoT devices.

• We design the scheme in detail and analyzed the correctness and security of the scheme. Simultaneously, after the performance analysis and comparison with related schemes, our scheme has higher efficiency in the stage of aggregation and encryption and decryption.

Abstract

Blockchain of Things (BCoT), as a new paradigm that incorporates blockchain with the Internet of Things (IoT), can address the privacy and extensibility issues in IoT systems and effectively enhance the data management of IoT devices. Asmost of theIoT devices are resource-constrained in terms of computing power, storage capacity, and energy consumption. Meanwhile,the enormous computational consumption in the consensus process of the blockchain makes it difficult to integrate with IoT closely and exert the great potential of BCoT. latterly, the ”cloud mining” mechanism has been proposed to address these issues, however,some potential problems still exist, such as data privacy and dishonest cloud mining pools, etc. In this paper, we propose a verifiable and privacy-preserving cloud mining pool selection scheme in BCoT (namely, VPP-CMPS). To obtain a better solution for cloud mining pool selection, we implement an improved time-locked puzzles technique to identify dishonest mining pools and perform the authenticity for mining pool selection.Afterwards,we obtain the privacy protection of the data during the entire selection process by adopting additively homomorphic ElGamal cryptosystem. Meanwhile, considering the resource-constrained case in IoT devices, we use a semi-honest cloud server to cooperate in dealing with the selection procedure, thereby reducing the computational overhead of IoT devices. Experimental results indicate that our scheme is more efficient and provides less computational cost.

Introduction

Over the last few years, the Internet of Things (IoT) has received a wide range of concerns from academia and industry [13]. The IoT is an expanding network of smart devices beyond traditional computing devices that deals with tasks from the cloud server and collects and sends data over the Internet [27]. Meanwhile, these IoT devices are forming some emerging applications, such as smart grid [21], [30], smart transportation [40], [25] and medical system [41] and so on. Nonetheless, the scalability, privacy, and security issues in IoT applications are gradually increasing with the expansion of the IoTs.

The emerging technology of blockchain technology has become a hot topic for both researchers and industry in the past few years, and Blockchain of Things (BCoT) [5], [20] is proposed by researchers as a new paradigm. As illustrated in Fig. 1, BCoT provides a new paradigm that combines blockchain with IoT, which not only increases the ability to exchange information between IoT devices, but also ensures the reliability of IoT data [22]. At the same time, it can also ensure the traceability of IoT device data in the blockchain platform [4]. Nonetheless,there still have some challenges to be solved in the process of combining blockchain with IoT. For instance, the consensus mechanism PoW [12], [43] in the blockchain requires to consume a large number of computing resources and energies. Specifically, each participating IoT device will play as a miner to continuously compute hash values to obtain the reward for successful mining. Nevertheless, the vast bulk of IoT devices have low performance and are constraintin terms of computational power, storage capacity, and energy resources. Moreover, the massive computing consumption of the blockchain will make it challenging to integrate with the Internet of Things well and it will not be able to give full play to the great potential of BCoT [28].

In IoT network, the storage space of edge devices is often limited, which is far from fulfilling the requirements of practical applications[44]. Researchers have proposed the cloud mining mechanism [26], [7] to figure out a better choice for BCoT. Cloud mining enables resource-constrained IoT devices to offload their computational tasks and storage loads to cloud servers or other edge devices [36]. Therefore, more and more resource-constrained IoT devices can join and help the consensus process through cloud mining [37]. However, with the exponential growth of IoT devices, there is a slim chance of a single device mining success. More and more individual IoT devices are willing to team up andform a mining pool to obtain a stable income [19]. Generally, high-performance mining pools will also have acceptable returns. To gain more benefit, an IoT device will always try to choose a high-performance mining pool to join. Nonetheless, there still exist issues of trust and privacy during the selection process of IoT devices, and some dishonest mining pools may lie about their high performance and high stakes to deceive IoT devices to volume up. In [15], [18], researchers have proposed the reputation mechanism to identify the honest nodes, but this generally requires a trusted third party to manage the reputation system. In addition, attacks from the outside cannot be ignored, which means that the private data of IoT devices and mining pools should be protected from being obtained by external adversaries [38]. Thus, a secure and reliable cloud mining pool selection scheme in BCoT needs to address privacy and trust issues.

To overcome the aforementioned challenges, we propose a verifiable and privacy-preserving cloud mining pool selection scheme in BCoT (namely VPP-CMPS scheme). Our proposal takes into account the transfer of private data between IoT devices and mining pools in BCoT. Simultaneously, for the sake of trust issue, we provide a verifiable approach to ensure that the mining pools can not misrepresent their performance, which is also applicable to other scenarios such as the selection of worker abilities in mobile crowdsensing [34], [32]. In addition, we consider the case of resource-constrained IoT devices and do not use a trusted third party to mitigate their computational overhead. Our main contributions are listed as below:

• We propose an improved time-lock puzzles protocol to judge whether the cloud mining pools are honest or not. The improved time-lock puzzles protocol enables a fast verification without being affected by the performance limitations of IoT devices while also helping IoT devices to select high-performance cloud mining pools in BCoT systems.

• By employing the additive homomorphic ElGamal cryptosystem, we achieve the privacy protection in data transmission and utilize a semi-honest cloud server to reduce the computational overhead of resource-constrained IoT devices.

• We give the concrete scheme in detail and analyze the correctness and security of the scheme. Simultaneously, after the performance analysis and comparison with related schemes [35], [6], it shows that our scheme provides a higher efficiency in the aggregation stage.

The rest of this paper is organized as follows. Section 2 gives the related work associated with cloud mining, worker selection, and privacy protection. Section 3 introduces some preliminaries used in this paper. In Section 4, we provide the system model, threat model, and design goals of our scheme. We give detailed protocol steps in Section 5. In Section 6, we present the correctness and security analysis of our scheme. Also, the performance evaluation is presented in Section 7. Finally, Section 8 draws a conclusion of the paper.