Proxy re-encryption with delegatable verifiability

Abstract

Proxy re-encryption is a public key encryption technique that allows a proxy to perform re-encryption without exposing the corresponding plaintext. As a result, proxy re-encryption has increased utility, and can be used in a number of fields including cloud computing. In previous proxy re-encryption schemes, a proxy is assumed to follow the protocol explicitly. However, this is far from the norm, and the assumption is not always true, especially in cloud computing where public cloud is considered untrusted. In this paper, we investigate the verifiability of the re-encryption process. Specifically, we first formalize the proxy re-encryption with delegatable verifiability and its corresponding security model. Then, we propose the first proxy re-encryption scheme with delegatable verifiability. Finally, security proofs of the proposal are also formally given in the proposed security models.