1. Quisquis: A New Design for Anonymous Cryptocurrencies 2019 Asiacrypt Blockchains Privacy
    Prastudy Fauzi, Sarah Meiklejohn, Rebekah Mercer and Claudio Orlandi
    [View PDF on eprint.iacr.org]
    [Show BibTex Citation]

    @misc{cryptoeprint:2018:990,
    author = {Prastudy Fauzi and Sarah Meiklejohn and Rebekah Mercer and Claudio Orlandi},
    title = {Quisquis: A New Design for Anonymous Cryptocurrencies},
    howpublished = {Cryptology ePrint Archive, Report 2018/990},
    year = {2018},
    note = {\url{https://eprint.iacr.org/2018/990}},
    }

Despite their usage of pseudonyms rather than persistent identifiers, most existing cryptocurrencies do not provide users with any meaningful levels of privacy. This has prompted the creation of privacy-enhanced cryptocurrencies such as Monero and Zcash, which are specifically designed to counteract the tracking analysis possible in currencies like Bitcoin. These cryptocurrencies, however, also suffer from some drawbacks: in both Monero and Zcash, the set of potential unspent coins is always growing, which means users cannot store a concise representation of the blockchain. Additionally, Zcash requires a common reference string and the fact that addresses are reused multiple times in Monero has led to attacks to its anonymity.

In this paper we propose a new design for anonymous cryptocurrencies, Quisquis, that achieves provably secure notions of anonymity. Quisquis stores a relatively small amount of data, does not require trusted setup, and in Quisquis each address appears on the blockchain at most twice: once when it is generated as output of a transaction, and once when it is spent as input to a transaction. Our result is achieved by combining a DDH-based tool (that we call updatable keys) with efficient zero-knowledge arguments.

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