## 6 Conclusions  
This study proposed a sidechain-based framework for building efficient, secure, and transparent digital asset trading platforms. The core idea lies in introducing a dedicated platform chain \(\mathbb{PC}_{M}\) as a private or consortium blockchain functioning as a sidechain to a well-established mainchain \(\mathbb{RC}\). This design allows the platform to inherit the stability and trustworthiness of the mainchain, without requiring any modifications to it, thereby significantly reducing the costs typically associated with establishing high levels of security and reliability. Moreover, by adopting a private or consortium model for the platform chain, the system benefits from faster consensus and transaction processing, customized blockchain configurations tailored to the specific needs of the platform, and greater adaptability to rapidly evolving business requirements. These characteristics make the proposed framework especially well-suited for dynamic digital asset trading environments that demand both performance and flexibility, alongside trust and verifiability. Controlling the behavior of the platform operator is a central concern in this study, particularly given the semi-centralized nature of private- or consortium-based blockchains. To ensure transparency and prevent operator misconduct, the proposed method introduces a dual-sidechain architecture. In this structure, only the hash values of transactions are initially recorded in \(\mathbb{PC}_{M}\), while the full transaction contents are disclosed and executed later in a paired dual platform chain \(\widehat{\mathbb{PC}}_{M}\), after the corresponding segment of \(\mathbb{PC}_{M}\) is finalized and anchored to \(\mathbb{RC}\). This architecture ensures that the operator cannot make decisions based on transaction content at the time of registration, effectively mitigating risks such as semantic-based censorship or favoritism. Once anchored, all registered hash values become irreversibly bound to their corresponding transactions when disclosed in \(\widehat{\mathbb{PC}}_{M}\), enabling transparent auditing. All operations are executed according to predefined smart contracts, which strictly constrain the range of actions that the platform operator can perform. Rather than minimizing centralized control in a general sense, the system explicitly limits operator authority by ensuring that all behaviors adhere to the logic encoded in immutable contracts. This safeguard is especially critical in private- or consortium-based settings, where the operator (e.g., \(t_{M}\)) would otherwise retain significant control over the platform. Through this approach, the framework effectively mitigates the risk of arbitrary or self-serving actions by the operator. To enhance scalability and efficiency, the method employs Merkle tree constructions that allow multiple transactions to be aggregated into a single root hash for registration. The framework defines the conditions under which such aggregation is valid, particularly when the transactions are logically and temporally independent. Since verifying such independence at the system level is inherently difficult, the framework delegates this responsibility to users. They are best positioned to judge whether their transaction depends on the outcome of another. To support this process, users are instructed to reference only transactions that have already been confirmed and finalized on the chain. The responsibility for managing transaction dependencies is explicitly assigned to users at the time of transaction creation. They must ensure that their transactions do not rely on the outcomes of other transactions that have not yet been finalized. This rule is essential to preserve the integrity of the system and applies regardless of whether transactions are registered individually or aggregated using Merkle trees. In addition, just as the platform operator is restricted to predefined smart contracts, users are also required to only create transactions through designated smart contract interfaces.