###### Abstract  
This study proposes a cost-effective and reliable blockchain-based approach for managing small-scale digital asset trading platforms. Instead of developing an independent blockchain, the proposed method constructs a sidechain anchored to established blockchains known for their stability and reliability, such as Bitcoin and Ethereum. In this study, we refer to these established blockchains serving as the mainchain for our sidechain as the _reference chain_. The proposed sidechain, termed the _platform chain_ in this paper, inherits the security and trust of the reference chain, while reducing operational costs and requiring no modifications to it. To enhance efficiency and privacy, the proposed method introduces a dual-sidechain architecture. The platform chain can be constructed either as a private blockchain or a consortium blockchain, depending on the specific operational requirements. In this architecture, only the hash values of transactions are recorded on the platform chain by default, while complete transaction content is disclosed through a _dual platform chain_ under controlled conditions. This enables strong privacy guarantees, alongside auditable transparency when needed. To evaluate the security and feasibility of our approach, we perform a comprehensive threat assessment, addressing critical threats such as operator-level manipulation, invalid or harmful user actions, collusion among system entities, and dishonest behavior by the auditor. Our results confirm that the proposed sidechain framework provides a secure, scalable foundation for digital asset trading platforms, effectively enhancing privacy and ensuring robust protection under various adversarial conditions. guidelines, privacy-preserving; reference chain; disclosure on demand  
30 March 202526 April 202526 May 202  
various areas such as prediction markets [15; 16; 17], fractional ownership [18; 19; 20], and digital asset exchanges [21; 22], driving innovations in blockchain-based asset trading. Blockchain technology offers several advantages for trading certain types of physical assets. For instance, if a physical asset can be tokenized on the blockchain and endowed with digital uniqueness, it can benefit from digitalization in various ways. Specifically, if token transactions on the blockchain network can be recognized as equivalents of actual asset transactions, this could significantly enhance the security and efficiency of the asset trading process [21; 23; 24]. In this study, we define the process of tokenizing and making assets tradable on the blockchain network as _digital assetization_, and the assets themselves as _digital assets_. Furthermore, platforms that facilitate the trading of such digital assets will be referred to as _Digital Asset Trading Platforms_ (DATPs). This paper explores a blockchain method for tokenizing specific physical assets and facilitating a DATP for such tokenized assets. In this study, we refer to the blockchain developed for this purpose as the _platform chain_ of the DATP. The primary goal of the platform chain is to tokenize physical assets, reduce transaction costs through token-based trading, and increase market accessibility. Furthermore, the platform chain seeks to increase trust in trading activities on the DATP utilizing the transparency and immutability of blockchain technology. Moreover, as observed in other business applications of blockchain [23; 25], the platform chain can enhance overall efficiency of DATPs by streamlining the transaction process through the integration of cryptocurrencies and smart contracts. To ensure the platform chain effectively supports DATP operations, certain conditions must be met to guarantee its reliability. These conditions are as follows:  
* **C1**: Transactions recorded on the platform chain are practically immutable and cannot be arbitrarily deleted or altered. * **C2**: Transactions recorded on the platform chain are acknowledged by the vast majority of participants.