Constraints-based and One-time Modification Redactable Blockchain

Immutability enables the blockchain to store data permanently, which is considered to be the most essential property to protect the security of blockchain technology. However, illegal content stored on the blockchain cannot be modified either. "The right to be forgotten" stipulates that the data subject has the right to request the data controller to delete personal data about him, and the controller is obliged to delete the personal data in a timely manner in such circumstances. Therefore, redactable blockchains are proposed to solve the aforementioned problems. The redactable blockchain relaxes the immutability of blockchains in a controlled manner. However, a participant who is granted the privilege to modify the blockchain, he/she may add inappropriate or malicious modifications to the content of historical blocks. In this article, we introduce a redactable blockchain where transaction owners restrict what editors can rewrite in transactions. When posting an editable transaction, the transaction owner indicates what can be edited and what cannot be edited in order to restrict a transaction modifier from making malicious changes to the content of the transaction. The modifier's changes to the transaction are then validated by the validator and any malicious changes that do not meet the requirements will fail to be validated. To counteract collusive attacks between modifiers and validators, they will be held accountable and penalized.