Compact Accountable Ring Signatures in the Plain Model

Accountable ring signatures close the gap between ring signatures and group signatures. They support a designated opener who can identify signers when necessary while allowing for the most excellent possible flexibility in selecting the ring. Accountable ring signatures were first informally defined by Xu and Yung at CARDIS 2004. They present a compiler that transforms a traditional ring signature scheme into an accountable one by using a trusted model on the smart cards. At ESORICS 2015, Bootle et al. introduced a formal security model for accountable ring signatures. In addition, they also present a generic construction for accountable ring signatures in the random oracle model. In terms of the security proof model, the plain model is preferable since it requires neither any assumptions that sometimes do not exist in practice nor any trusted setup assumptions. Until now, there has been no construction of accountable ring signatures in the plain model, even with a linear signature size. In this paper, we present the first generic construction of accountable ring signature schemes that have the logarithmic signature size and are secure in the plain model using standard assumptions.