Cryptocurrency allows for immutable and transparent payments in the decentralized manner. The transparency nature inevitably leads to leakage of users’ private information. Although existing schemes provided privacy preservation in cryptocurrencies, they fail to consider regulation and facilitates conducting illegal activities. To solve this problem, several works aimed at striking a balance between preservation of users’ privacy and identification of malicious users. However, they introduced a central authority (which runs counter to the decentralization design of cryptocurrencies), and reveals only the pseudonym of a malicious user other than her/his real identity due to lack of authentication. In this work, we propose PICTURE, a privacy-preserving cryptocurrency with threshold authentication and regulation. In PICTURE, a user registers to a group of authorities (instead of a centralized one) who cooperatively issue the user with a master account which is actually a randomizable signature. The user randomizes the master account to be authenticated and transact anonymously. Besides, the transaction contains a record, with which the authorities can reveal the user’s identity (that is used in registration) in the threshold way. Our construction enables the user to prove that the record is well-formed with only a standard Schnorr’s protocol, leading to lower overheads compared with existing works. We provide a formal security proof to demonstrate that PICTURE is secure, and conduct a comprehensive performance evaluation to show that PICTURE is ready to be deployed in real world.

中文翻译：

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具有阈值身份验证和监管的隐私保护加密货币


加密货币允许以去中心化的方式进行不可变且透明的支付。透明性不可避免地导致用户隐私信息的泄露。尽管现有方案提供了加密货币的隐私保护，但它们没有考虑监管并促进了非法活动的进行。为了解决这个问题，一些工作旨在在保护用户隐私和识别恶意用户之间取得平衡。然而，他们引入了一个中心化机构（这与加密货币的去中心化设计背道而驰），并且由于缺乏身份验证，只暴露了恶意用户的假名，而不是她/他的真实身份。在这项工作中，我们提出了 PICTURE，一种具有阈值身份验证和监管的隐私保护加密货币。在图片中，用户注册到一组权威机构（而不是中心化机构），这些权威机构合作向用户颁发一个主帐户，该帐户实际上是一个可随机签名。用户随机分配主账户进行身份验证并匿名交易。此外，交易中还包含一条记录，当局可以通过该记录以阈值方式泄露用户的身份（用于注册）。我们的构造使用户能够仅使用标准 Schnorr 协议来证明记录格式良好，从而与现有工作相比降低了管理费用。我们提供正式的安全证明来证明 PICTURE 是安全的，并进行全面的性能评估以表明 PICTURE 已准备好在现实世界中部署。