Paper 2015/112

Re-encryption Verifiability: How to Detect Malicious Activities of a Proxy in Proxy Re-encryption

Satsuya Ohata and Yutaka Kawai and Takahiro Matsuda and Goichiro Hanaoka and Kanta Matsuura

Abstract

In this paper, we introduce a new functionality for proxy re-encryption (PRE) that we call re-encryption verifiability. In a PRE scheme with re-encryption verifiability (which we simply call verifiable PRE, or VPRE), a receiver of a re-encrypted ciphertext can verify whether the received ciphertext is correctly transformed from an original ciphertext by a proxy, and thus can detect illegal activities of the proxy. We formalize the security model for a VPRE scheme, and show that the single-hop uni-directional PRE scheme by Hanaoka et al. (CT-RSA 2012) can be extended to a secure VPRE scheme.