STPCH: strongly traceable policy-based chameleon hash for blockchain rewriting

Abstract Policy-based chameleon hash (PCH) is a useful primitive in blockchain rewriting. It allows a party to compute a chameleon hash based on an access policy, and another party who possesses sufficient privileges satisfying the access policy to rewrite the hashed object. However, PCH lacks strong traceability. The chameleon trapdoor holder may abuse their rewriting privilege and maliciously rewrite the hashed object without being identified. In this paper, we introduce a new primitive called strongly traceable policy-based chameleon hash (STPCH for short). We first present a generic framework of STPCH. Then, we present a practical instantiation, show its practicality through implementation and evaluation analysis.