applied sciences  
A Privacy-Enabled, Blockchain-Based Smart Marketplace  
[PERSON] 1,*, *, [PERSON] 2, *, [PERSON] 3, *, [PERSON] 4, *, [PERSON] 4, *, and [PERSON] 5,*, *,  
and elliptic curve cryptography (ECC) have been used to provide transactional data privacy [5; 6; 8]. The Bitmessage [9] method of decentralized peer-to-peer (P2P) message authentication and delivery based on the proof-of-work (PoW) consensus algorithm was adopted by many approaches, such as those in [6; 10], to provide anonymity in a trustless network by broadcasting encrypted messages in messaging streams.  
With respect to the use of the above approaches to accomplish the desired privacy parameters in a blockchain-based SMP, the following issues and limitations have been identified:  
* The use of multiple accounts and Merkle trees, as in [6; 7], is not very successful against blockchain analysis and other similar techniques [1; 2; 11]. Thus, they can be used to link multiple accounts of a participant to infer the participant's identity. On the other hand, the implementation of a Merkle tree in a blockchain-based network, such as the Ethereum network, may inevitably require a large-scale computing resource [12].
* Cryptographic approaches, such as the ECDSA and ECC [5; 6; 8], utilizes time-consuming procedures, such as bilinear pairings [13; 14]. The process may lead to high computational and storage overheads, thus posing practical problems due to the resource constraint nature of the smart gateway in smart homes [15; 16; 17].
* Instead of using an encryption method that often makes the content of the encrypted blocks mutually dependent, Bitmessage encrypts each block individually. Through this, the adversary will be able to rearrange the message blocks in such a way that the recipient can interpret it as a legitimate message [18]. With this, the adversary can infer the transactional data stored in the blocks as well as identify the participants involved in the transactions.  
The situation is further aggravated when one takes into account the type of trading mechanism used in the SMP. The trading approaches may allow a participant to have only a single (one-to-one) or multiple (one-to-many) simultaneous transactions. The objective of this work is to ensure the anonymity and untraceability of the participant and provide transactional data privacy under a one-to-many trading model. To achieve these goals, a novel lightweight scheme is presented that utilizes a pair of public/private IDs with anonymous messaging streams. Security analysis and experimental evaluation of the proposed solution is performed to evaluate and compare it against existing state-of-the-art schemes.  
_Contributions:_ The following are the contributions of this paper:  
* A protocol is presented to ensure the participant's anonymity and untraceability during one-to-many trading in the SMP, using public/private pairs of communicating session IDs.
* A protocol is also presented to ensure privacy preservation of the transactional data of the participants during one-to-many trading in the SMP at a reduced computational overhead.
* Our results show that the proposed system is more resilient against identity-based attacks such as blockchain analysis attacks and achieves a lower probability of success of the adversary compared with that in [6; 7] with a reduced computational overhead.  
_Organization of the Paper:_ The rest of this paper is organized as follows. Section 2 provides an overview of the related work. In Section 3, we present the system model. Section 4 describes the proposed security protocol. Section 5 discusses the security analysis. Section 6 explains the experimental analysis and results, and Section 7 presents the conclusions.