Cryptocurrencies have the potential to enable socioeconomic growth throughout the world by offering easier access to capital and financial services. However, many virtual asset service providers (VASPs) that offer cryptocurrency services lack identity management and can be accessed anonymously, which has led to their services being exploited by criminal activities such as money laundering and illegal foreign exchange. Such crimes have a negative impact on socioeconomic sustainability. Building identity systems on blockchains can help VASPs improve their identity management to combat cryptocurrency-based crimes so VASPs can better serve the social economy and achieve their sustainability goals. However, existing solutions have privacy problems because the identity provider can associate users’ identities with their wallet accounts. In addition, there is currently no solution that can support all public blockchains unconditionally, as current solutions can only support EVM-compliant blockchains or require additional work to support new blockchains. This article proposes a KYC (know your customer)-compliant identity scheme based on Ethereum using Merkle trees and smart contracts. The identity and wallet accounts are linked by the user rather than the KYC provider so, in general, no one but the user knows the association between the wallet accounts and the identity, which protects privacy. For suspicious accounts, supervisors can trace their identities and thus achieve supervision. In addition, the scheme supports identifying accounts on all public blockchains by using Merkle trees and smart contracts to bind accounts on multiple blockchains to one identity and no extra work is required. Moreover, the scheme supports users to prove that their attributes meet the requirements of VASPs by adopting the BBS+ signature and the Sigma protocol.

Alliance chain has gained widespread popularity in industrial and commercial fields due to its multi-centralization and node manageability. Current implementations of the alliance chain suffer from scalability obstacles, such as communication congestion and throughput drop, when the number of nodes increases. In this paper, a novel dynamic transaction confirmation sharding protocol is proposed, which improves transaction processing efficiency by partitioning nodes and assigning different transactions to different shards. It utilizes dynamic transaction confirmation consensus as a sharding intra-consensus mechanism to minimize message size and package transactions into microblocks, which modifies communication content during transaction propagation among shards and reduces network congestion and shard reconfigure cost. The protocol leverages a review system and reputation model to identify and punish malicious nodes and also incorporates a verifiable random function for node configuration, which ensures a sufficient number of honest nodes within the shard and prevents repeated consensus processes. Simulation results show that the proposed protocol outperforms mainstream used permissioned chain sharding protocols Attested HyperLedger and Sharper, achieving a throughput improvement of at least 20%. This protocol is suitable for scenarios requiring high throughput and reliability in industrial and commercial fields such as finance, logistics, and supply chain management. Even if the number of alliance chain nodes increases to the usual maximum, or there are some faulty nodes, the protocol can still maintain stable performance.

Cryptocurrencies offer various benefits in terms of privacy protection and cross-border transactions, but they have also been used for illicit activities such as money laundering due to their anonymous nature and the difficulty of cross-border regulation. Additionally, the unethical actions of some virtual asset service providers (VASPs), such as rug pulls and the embezzlement of user funds, have further eroded the trust between users and VASPs. Implementing identity management on blockchains can help restore trust between users and VASPs. However, current solutions have privacy concerns as identity providers have access to the asset balances and transaction records of each user’s wallet account, and no solution can support all public blockchains unconditionally. To address these issues, this paper proposes a multi-chain aggregated identity scheme. In this scheme, the identity provider will issue a non-fungible token (NFT) for users who have undergone verification, and wallet accounts from different blockchains will be added to a cryptographic accumulator. The accumulator value is then bound to the identity NFT through a smart contract by the user. This allows the user to prove to others that the identity of the wallet account owner has been verified. The use of accumulators also allows users to combine proof for multiple wallets into a single proof, which significantly improves the efficiency and provides a way for VASPs such as centralized exchanges to demonstrate Proof of Reserves (PoR) to users. Importantly, this scheme preserves privacy as neither the identity provider nor the VASPs can link the user’s real identity with the wallet accounts. Only regulators can access the user’s identity data held by the identity provider and the user’s wallet account held by the VASP to link real identities with wallet accounts for the purpose of sanctions or criminal investigations. Additionally, the scheme supports all blockchains by allowing wallet accounts from any public blockchain to be added to the accumulator. Furthermore, the NFT implementation in the scheme helps prevent identity loss or theft, as it can only be transferred by the identity provider.