Verifying the Integrity of Private Transaction Information in Smart Contract using Homomorphic Encryption

Blockchain-based Smart Contract allows reliable enforcement of the programmatically specified agreement between distributed agents. However, during the process of verifying the result of transaction execution with distributed consensus protocol, private information such as fund amount being transferred can be exposed to others. To hide such sensitive information while keeping the integrity of the Smart Contract instances, we employ a homomorphic encryption technique. With this encryption technique, the validity of the arithmetic operation in a transaction can be checked without decrypting the operands. For instance, a remaining balance after fund transfer can be validated while the exact amount of the transferred fund and the final balance are kept in a ciphertext. In this work, we discuss the novel system architecture for verifying Smart Contracts instances with homomorphic encryption and evaluate its efficiency.