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BPCEX: Towards Blockchain-based Privacy-preserving Currency Exchange

Privacy-preserving currency exchange between different cryptocurrencies on blockchain remains an open problem as the existing currency exchange schemes cannot provide anonymity of traders or confidentiality of exchange amount. To solve this problem, we introduce BPCEX: a privacy-preserving currency exchange scheme which protects traders' identities and the exchange amount, by usage of techniques including linkable ring signature, range proof, Diffie-Hellman key ex¬change, Pedersen commitment and UTXO swap. In BPCEX, the traders' identities are hidden to verifiers and dealmakers, while the exchange amounts are hidden to the verifiers. BPCEX supports floating exchange rate, partial deal and public verifica¬tion, without additional confirmation of traders, which improves the success rate and shortens the waiting time of the deal. Moreover, BPCEX is compatible with the auditable privacy-preserving blockchain system, which realizes the traceability of traders' identities and the exchange amount to prevent money laundering and illegal exchange, making BPCEX suitable in real-life applications, including currency market and stock market.