A Regulation Scheme Based on the Ciphertext-Policy Hierarchical Attribute-Based Encryption in Bitcoin System

In Bitcoin financial system, a user's privacy is supposed to be protected by means of anonymity. However, the anonymity makes illegal trades possible because nobody is able to reveal the real identities of the illegal users. In this paper, we propose a regulation scheme based on the ciphertext-policy hierarchical attribute-based encryption (CP-HABE). In the scheme, users' identities are encrypted by using access policy and are contained in their transaction. A type of user is defined as the dependable regulation node, which is responsible for the regulation of transactions and encrypted identities. A new signature algorithm instead of the elliptic curve signature is adopted to generate wallet key pairs, this establishes a connection between wallet addresses and encrypted identities. When a transaction is doubted to involve illegal activities, the authorized regulation nodes are capable of revealing the users' real identities and add the illegal identities to a public blacklist. Our system is based on a new CP-HABE scheme which is proved to be secure against chosen-plaintext attack in the standard model under the Bilinear Diffic-Hellman Exponent assumption. Finally, we give a performance analysis of our system. The proposed regulation system can reveal criminals' identities undertaking illegal activities.