Redactable signature schemes for trees with signer-controlled non-leaf-redactions

Abstract

Redactable signature schemes (RSS) permit to remove parts from signed documents, while the signature remains valid. Some RSSs for trees allow to redact non-leaves. Then, new edges have to be added to the tree to preserve it’s structure. This alters the position of the nodes’ children and may alter the semantic meaning encoded into the tree’s structure. We propose an extended security model, where the signer explicitly controls among which nodes new edges can be added. We present a provably secure construction based on accumulators with the enhanced notions of indistinguishability and strong one-wayness.