# Supervised Blockchain Anonymous Transaction Model Based on Certificateless Signcryption
## 1 Introduction  
Since [PERSON] proposed Bitcoin [1] in 2008, blockchain technology, as its underlying architecture, has been widely applied in various fields such as financial services and the Internet of Things, thanks to its core features of decentralization, transparency, and immutability. However, the public transparency of blockchain also brings significant privacy risks. Research shows that approximately 67% of Bitcoin users can be de-anonymized through methods such as transaction graph analysis and IP address association, thereby exposing sensitive information such as their asset flows and consumption habits. Therefore, the protection of privacy in blockchain transactions has been a focal point of interest in both academia and industry. Currently, blockchain transaction systems commonly use a model of public ledgers and multi-party confirmation to achieve a pseudo-anonymization of user identities. However, this mechanism has fundamental flaws, as attackers can break anonymity through techniques such as network analysis and address clustering. To enhance anonymity, scholars have proposed various anonymity-enhancing technologies, such as Zerocash [2],Moreno [3], and Dash [4]. However, while these technologies achieve complete anonymity of user identity information, they also hinder regulatory needs such as anti-money laundering (AML) and financial crime investigations, leading to transaction bans on privacy coins by regulatory agencies in multiple countries. Therefore, balancing anonymity and regulatory compliance in blockchain transactions has become an important research topic. Currently, there are two main models for blockchain transactions: the Unspent Transaction Output (UTXO) model and the account model. In the UTXO model, asset movement is viewed as a directed acyclic graph between users, and a user's balance is represented by the state of all UTXOs associated with them in the system. This means there is a one-to-many relationship between balance and address, as seen in Bitcoin. There has been a significant amount of research, both domestically and internationally, addressing the transaction privacy issues related to the UTXO model, primarily focusing on protecting the identity privacy of transaction users and the transaction amounts. The technologies employed include mixing techniques, ring signatures, vector commitments, and zero-knowledge proofs, aimed at achieving confidentiality and untraceability of transaction amounts. In contrast, the account model maintains a global state of all accounts and their balances, which are updated in real time as transactions occur. This results in a one-to-one correspondence between each account balance and its address, as seen in Ethereum. Consequently, most privacy-preserving schemes designed for the UTXO model are not applicable to the account model. Existing research on account model privacy heavily relies on centralized regulatory authorities, which not only contradicts the principle of decentralization in blockchain but also poses risks of single point key leakage or abuse of power. In response to the above issues, this paper proposes a supervised blockchain anonymous transaction model based on certifiateless signcryption under the account model. By integrating certificate-free cryptography with a distributed regulatory mechanism, it achieves a balance between user privacy protection and transaction supervision. The main contributions are outlined below. 1. A supervised blockchain anonymous transaction model based on certifiateless signcryption is proposed--CLSC_SAT. It not only achieves anonymity of transaction users and confidentiality of transaction amounts but also ensures the entire process is in compliance with regulations, thus striking a balance between transaction privacy protection and regulatory requirements. 2.