Non-transferable proxy re-encryption for multiple groups

Abstract

In proxy re-encryption (PRE) scheme, the message is sent by a delegator to a delegatee with help of the trusted third party proxy without knowing the existing plaintext. It is known that non-transferable PRE schemes solve some problems of the naive PRE schemes. Some non-transferable PRE scheme is extended to group-based schemes, where the proxy diverts a ciphertext for a group into another group, but the existing schemes have the proxy colluding problem. To resolve the proxy colluding problem for group-based PRE schemes, we propose a non-transferable PRE scheme for multiple groups. In our scheme, there are three sub-processes, which are based on a non-transferable PRE scheme and a group signature. We show that our scheme provides the security for a delegator Alice, a delegatee Bob in the same group with Alice, and another delegatee Charlie in a different group from Alice.