  Blockchain rewriting with fine-grained access control allows a user to create
a transaction associated with a set of attributes, while another user (or
modifier) who possesses enough rewriting privileges from a trusted authority
satisfying the attribute set can rewrite the transaction. However, it lacks
accountability and is not designed for open blockchains that require no trust
assumptions. In this work, we introduce accountable fine-grained blockchain
rewriting in a permissionless setting. The property of accountability allows
the modifier's identity and her rewriting privileges to be held accountable for
the modified transactions in case of malicious rewriting (e.g., modify the
registered content from good to bad). We first present a generic framework to
secure blockchain rewriting in the permissionless setting. Second, we present
an instantiation of our approach and show its practicality through evaluation
analysis. Last, we demonstrate that our proof-of-concept implementation can be
effectively integrated into open blockchains.
