A Framework for Efficient Signatures, Ring Signatures and Identity Based Encryption in the Standard Model

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In this paper, the authors present a generic framework for constructing efficient signature schemes, ring signature schemes, and identity based encryption schemes, all in the standard model (without relying on random oracles). They start by abstracting the recent work of Hohenberger and Waters (Crypto 2009), and specifically their "Prefix method". They show a transformation taking a signature scheme with a very weak security guarantee (a notion that they call a-priori-message unforgeability under static chosen message attack) and producing a fully secure signature scheme (i.e., existentially unforgeable under adaptive chosen message attack).