A Secure and Efficient Conditional Anonymous Scheme for Permissionless Blockchains

Abstract

The conditional anonymous scheme for permissionless blockchains satisfies anonymity and traceability simultaneously. Specifically, though transactions are published anonymously, the supervision authority can still trace the identity of the transaction producer when there is a suspicious transaction. However, the uncontrolled randomness employed in existing schemes leads to security risks and unsatisfying storage efficiency. In order to deal with these problems, we propose a secure and efficient conditional anonymous scheme in permissionless blockchains in this paper. In particular, we employ the bilinear ring signature to avoid security risks such as secret key leakage, covert communication and hidden persistent storage. Subsequently, the double-chain structure is introduced to significantly improve the storage efficiency, in which a supervision chain storing users’ hidden identity information is built on top of permissionless blockchains. We demonstrate the security and efficiency of our conditional anonymous scheme by numerous analyses and experiments.