Privacy-Preserving Pre-Consensus Protocol for Blockchains

A blockchain is a technology that allows transactions to be processed and committed data to be shared among participants without a central server. To implement applications among restricted parties with permission such as asset sales and trades, a special type of blockchain system called a private blockchain is used. Additionally, the demand for privacy preservation where sensitive information such as the trade amounts and balances is not disclosed is increasing. However, privacy preservation in a typical blockchain setting is difficult because it prevents parties that are not involved in the transaction from checking the correctness of the transaction being processed, which may lead to unintended or invalid transactions. To address this issue, herein we propose a protocol that allows the consistency with regard to the transaction amount and the balance to be checked without disclosing their values. Specifically, we exploit a homomorphic encryption to encrypt the transaction amount and balance. Thus, the correctness of a transaction can be publicly verified by the parties using the zero-knowledge proof without a trusted third party.