Proof of reserves and non-double spends for Chaumian Mints

Abstract: E-cash was invented in 1982 by David Chaum as an anonymous cryptographic electronic cash system based on blind signatures. It is not a decentralized form of money as Bitcoin. It requires trust on the server or Mint issuing the e-cash tokens and validating the transactions for preventing double spends. Moreover, the users also need to trust the Mint to not debase the value of e-cash tokens by Minting an uncontrolled number. In particular, this is critical for e-cash tokens representing a note of another asset as a currency, or bitcoin, or another cryptocurrency. Thus it would be suitable to implement a public auditing system providing a proof of reserves that ensures that the Mint is not engaging into a fractional reserve system. In this article we describe how to implement a proof of reserves system for Chaumian Mints. The protocol also provides a proof of non-double spends.