A Framework for Unique Ring Signatures

We propose a simple, general, and unified framework for constructing unique ring signaturesthat simplify and capture the spirit of linkable ring signatures. The framework, which can beefficiently instantiated in the random oracle and the standard model, is obtained by generalizingthe Bellare-Goldwasser “PRF made public” paradigm. Security of the first instantiation can betightly related to the DDH problem. The scheme leads to the most efficient linkable/unique ringsignature in the random oracle model, for a given level of provable security. The second onebased on stronger assumptions partly simplifies and slightly improves sublinear size traceablering signature of Fujisaki. Both of the improvements would be difficult without the generalframework in hand.