Revocable identity‐based matchmaking encryption in the standard model

Abstract

Identity-based Matchmaking Encryption (IB-ME) is an extension notion of matchmaking encryption (CRYPTO 2019), where a sender and a receiver can specify an access policy for the other party. In IB-ME, data encryption is performed by not only a receiver identity but also a sender's encryption key. Nevertheless, previous IB-ME schemes have not considered the problem of efficient revocation. Hence, the authors introduce a new notion of revocable IB-ME (RIB-ME) and formalise the syntax and security model of RIB-ME. In particular, the authors give an effective and simple construction of RIB-ME in the standard model, whose security is reduced to the hardness of decisional bilinear Diffie-Hellman problem and computational Diffie-Hellman problem. In addition, the authors show two extensions of our RIB-ME scheme to consider chosen-ciphertext security and forward privacy. K E Y W O R D S cryptography, public key cryptography 1 | INTRODUCTION Matchmaking Encryption: At CRYPTO 2019, Ateniese et al. [1,2] proposed the notion of matchmaking encryption (ME), which provides privacy-preserving policy matching over both the sender and receiver. In particular, sender S and receiver R can both specify policies that the other party must satisfy in order for the message to be revealed. In particular, S described by σ encrypts a message m under a specified policy R, and produces a corresponding ciphertext CT that associates with both σ and R. By also specifying a policy S that S should satisfy, R described by ρ uses its decryption key that is related to ρ to reveal the encrypted message from his target sender S. Thus, we have � If R cannot decrypt CT, it is a "mismatch case". This implies that either S is not accepted by R's policy (i.e., SðσÞ ¼ 0) or R is not accepted by S's policy (i.e., RðρÞ ¼ 0).� If R can decrypt CT, it is a "match case". This implies that both S is accepted by R's policy (i.e., SðσÞ ¼ 1), and R is accepted by S's policy (i.e., RðρÞ ¼ 1).