Ordered Multi-Signatures with Public-Key Aggregation from SXDH Assumption

An ordered multi-signature scheme allows multiple signers to sign a common message in a sequential manner and allows anyone to verify the signing order of signers with a public-key list. In this work, we propose an ordered multi-signature scheme by modifying the sequential aggregate signature scheme by Chatterjee and Kabaleeshwaran (ACISP 2020). Our scheme offers compact public parameter size and the public-key aggregation property. This property allows us to compress a public-key list into a short aggregated key. We prove the security of our scheme under the symmetric external Diffie-Hellman (SXDH) assumption without the random oracle model.