Practical and secure policy-based chameleon hash for redactable blockchains
Nan Li, Yingjiu Li, Mark Manulis, Yangguang Tian, Guomin Yang · The Computer Journal · 2024
Abstract Policy-based chameleon hash functions have been widely proposed for its use in blockchain rewriting systems. They allow anyone to create a mutable transaction associated with an access policy, while an authorized user who possesses sufficient rewriting privileges from a trusted authority satisfying the access policy can rewrite the mutable transaction. However, existing chameleon hash functions lack certain fundamental security guarantees, including forward security and backward security. In this paper, we introduce a new primitive called forward/backward-secure policy-based chameleon hash (FB-PCH for short). We present a practical instantiation. We prove that the proposed scheme achieves forward/backward-secure collision-resistance, and show its practicality through implementation and evaluation analysis.