Aggregate Cash Systems: A Cryptographic Investigation of Mimblewimble
https://eprint.iacr.org/2018/1039Abstract: Mimblewimble is an electronic cash system proposed by an anonymous author
in 2016. It combines several privacy-enhancing techniques initially envisioned for Bitcoin,
such as Confidential Transactions (Maxwell, 2015), non-interactive merging of transactions
(Saxena, Misra, Dhar, 2014), and cut-through of transaction inputs and outputs (Maxwell,
2013). As a remarkable consequence, coins can be deleted once they have been spent while
maintaining public verifiability of the ledger, which is not possible in Bitcoin. This results
in tremendous space savings for the ledger and efficiency gains for new users, who must
verify their view of the system.
In this paper, we provide a provable-security analysis for Mimblewimble. We give a precise
syntax and formal security definitions for an abstraction of Mimblewimble that we call
an aggregate cash system. We then formally prove the security of Mimblewimble in this
definitional framework. Our results imply in particular that two natural instantiations
(with Pedersen commitments and Schnorr or BLS signatures) are provably secure against
inflation and coin theft under standard assumptions.
