Generic Traceable Proxy Re-encryption and Accountable Extension in Consensus Network

Abstract

Proxy re-encryption provides a promising solution to share encrypted data in consensus network. When the data owner is going to share her encrypted data with some receiver, he will generate re-encryption key for this receiver and distribute the key among the consensus network nodes following some rules. By using the re-encryption key, the nodes can transform the ciphertexts for the receiver without learning anything about the underlying plaintexts. However, if malicious nodes and receivers collude, they can obtain the capability to decrypt all transformable ciphertexts of the data owner, especially for multi-nodes setting of consensus network. In order to address this problem, some “tracing mechanisms” are naturally required to identify misbehaving nodes and foster accountability when the re-encryption key is abused for distributing the decryption capability. In this paper, we propose a generic traceable proxy re-encryption construction from any proxy re-encryption scheme, with the twice size ciphertext as the underlying proxy re-encryption scheme. Then our construction can be instantiated properly to yield the first traceable proxy re-encryption with constant size ciphertext, which greatly reduces both the communication and storage costs in consensus network. Furthermore, we show how to generate an undeniable proof for node’s misbehavior and support accountability to any proxy re-encryption scheme. Our construction is the first traceable proxy re-encryption scheme with accountability, which is desirable in consensus network so that malicious node can be traced and cannot deny his leakage of re-encryption capabilities.