Multisignatures as Secure as the Diffie-Hellman Problem in the Plain Public-Key Model

A multisignature scheme allows a group of signers to cooperate to generate a compact signature on a common document. The length of the multisignature depends only on the security parameters of the signature schemes and not on the number of signers involved. The existing state-of-the-art multisignature schemes stiffer either from impractical key setup assumptions, from loose security reductions, or from inefficient, signature verification. In this paper, we present two new multisignature schemes that address all of these issues, i.e., they have efficient signature verification, they are provably secure in the plain public-key model, and their security is tightly related to the computation and decisional Diffie-Hellman problems in the random oracle model. Our construction derives from variants of EDL signatures.