Cipherchain: A Secure and Efficient Ciphertext Blockchain via mPECK

: Most existing blockchain schemes are based on the design concept “openness and transparency” to realize data security, which usually require transaction data to be presented in the form of plaintext. However, it inevitably brings the issues with respect to data privacy and operating performance. In this paper, we proposed a novel blockchain scheme called Cipherchain, which can process and maintain transaction data in the form of ciphertext while the characteristics of immutability and auditability are guaranteed. Specifically in our scheme, transactions can be encrypted locally based on a searchable encryption scheme called multi-user public key encryption with conjunctive keyword search (mPECK), and can be accessed by multiple specific participants after appended to the globally consistent distributed ledger. By introducing execution-consensus-update paradigm of transaction flow, Cipherchain cannot only make it possible for transaction data to exist in the form of ciphertext, but also guarantee the overall system performance not greatly affected by cryptographic operations and other local execution work. In addition, Cipherchain is a promising scheme to realize the technology combination of “blockchain+cloud computing” and “permissioned blockchain+public blockchain”.