Identity-Based Matchmaking Encryption Secure Against Key Generation Center

Identity-based matchmaking encryption (IB-ME) is a generalization of identity-based encryption (IBE), in which both the sender and receiver can specify the target identity. The key escrow problem, in which the authority is concentrated in the key generation center, has been pointed out as one of the most important issues, when implementing IBE in the real world. Recently, an approach to solve the key escrow problem in IBE has been proposed by introducing a new entity called an Identity Certificate Authority (ICA), which decentralizes the authority. In this paper, we extend the above approach to solve the key escrow problem for IBE to the IB-ME setting. Specifically, we first propose a new formalization of IB-ME solving the key escrow problem (by introducing ICA in its formulation). This new type of IB-ME is called blind IB-ME with certified identities. Then, we provide a concrete construction of blind IB-ME with certified identities based on the standard assumptions over bilinear groups. Finally, we implement our proposed scheme and demonstrate that it is practically efficient compared with existing schemes.